The Boulder Timeline was made possible with underwriting support from WK Real Estate, Boulder.




The Fountain Formation was deposited in a series of alluvial fans.  This geologic unit includes the Flatirons, Boulder’s iconic red mountain backdrop.

The Front Range rose, eroded and rose again.

15,000 YEARS AGO
Ice Age glaciation and continuing stream erosion began to give the high peaks and the foothills the shapes they have today.

For thousands of years, the Boulder Valley was home to several tribes of Native Americans.

1600-1800s European colonization forced many Native American tribes further west. The Arapaho and Cheyenne, for example, moved from the Great Lakes Region to the Plains. The nomadic Southern Arapaho, led by Chief Niwot, often wintered in Boulder Valley.

Read more about The Indigenous Period of Colorado


Gold Discovered

Gold was discovered south of Denver, stimulating the Pikes Peak Gold Rush. The first Anglo-European settlers arrived at the mouth of Boulder Canyon, breaching the borders of Arapaho territory as defined by the Fort Laramie Treaty. Chief Niwot granted the group the right to spend the winter and then leave, but the settlers did not honor that agreement to leave.


Gold Triggered Development

Gold was discovered near Gold Hill, west of Boulder, and the Boulder City Town Company was formed on February 10 and Boulder became a supply base for the miners. The town grew to a population of 343 by 1870, with these settlers defying the terms of the Fort Laramie Treaty. The first irrigation ditch in Boulder County was dug, and coal was discovered in the Marshall area southeast of Boulder. 


Colorado Territory

Congress voted to create the new Colorado Territory. The admission of new territories was a contentious issue in Congress until the Civil War, which cleared the way for the admission of the free Colorado Territory.


Congregational Church

The Congregational Church began to build and move to 11th and Pine Street, at the site of what is now the Carnegie Library, next door to the Museum of Boulder. The hillside spot was chosen so that the bell tower (the County’s first) would be visible to residents for miles around.



Sand Creek Massacre

Chief Niwot and an estimated 70–500 Native Americans, about two-thirds of whom were women and children, died at the hands of Colorado troops, including officers and men from Boulder, at the Sand Creek Massacre. Colonel John Chivington gained infamy for leading a 700-man force of the Colorado Territory militia at the massacre in November 1864.


Boulder City Incorporated

The Boulder City Town Company had been formed by a settler, A.A. Brookfield, in February 1859. At that time, the settlement was part of the Nebraska Territory. In 1861, a federal bill established the Territory of Colorado. The town was initially incorporated in November 1871 in violation of the Treaty of Fort Laramie. In 1880, the town passes the 3,000 population mark, making it eligible for incorporation, and in 1882 Boulder is officially incorporated as a 2nd class town.



Colorado became the 38th state on August 1. Known as the Centennial State, it was incorporated 100 years after the signing of the Declaration of Independence.


University of Colorado

The University of Colorado opened on land donated by prominent residents. CU’s first graduating class consisted of men in 1882 and the only building on campus was Old Main. State Preparatory School (later Boulder High) was founded as part of University because of a lack of adequately prepared high school graduates.


Mary Rippon

Mary Rippon was appointed first woman professor at CU, making her the first female to teach at a state university in the country.



Daily Camera Founded

The Boulder Camera was founded to cover local news and became a daily the next year. Still in publication, today it is known as the Daily Camera.


Right to Vote

Women in Colorado won the right to vote, 26 years before the passage of the 19th Amendment, due to a powerful statewide organizing effort in advance of the popular referendum.


100-Year Flood

Sixty straight hours of warm Spring rain combined with a rapid snowmelt to create a 100-year flood that ravaged Boulder. The floodwaters covered most of the town, inundating much of downtown, destroying buildings and bridges. Boulder was split in two as transportation and communication services were knocked out. Reconstruction began soon after the flood but proved an arduous process.



Colorado Sanitarium

The Colorado Sanitarium, a branch of Dr. J.H. Kellogg’s Battle Creek Sanitarium in Michigan, was dedicated in Boulder, originally to combat tuberculosis in Boulder’s dry climate and high altitude.


Boulder’s 311 Mapleton property at the base of Mt. Sanitas has long had a healthcare focus: before it was Boulder Community Hospital’s Mapleton Center, and before it was Boulder Memorial Hospital, it was a sanatorium. Patients at the sanitorium rested in wheelchairs as they took in the scenery and fresh air of Colorado. Founded in the 1890s by the Seventh-Day Adventist Church and Dr. John Harvey Kellogg (yes, the Kellogg we now associate with cereal), the sanitarium emphasized exercise (including hikes up Mt. Sanitas), alternative treatments like electroshock and hydrotherapy, and the power of a good diet. On the advice of Dr. Kellogg, patients ate strict vegetarian diets and an abundance of cereals and grains. In fact, an on-site factory produced the corn flakes and other health foods for which the Kellogg Company is now known.

Many early patients at “the San” had tuberculosis, the “White Plague” that Americans so greatly feared in the 1800s. Doctors believed that sunshine, fresh air, and altitude were essential to treating the disease, and encouraged tuberculosis patients to move from the humid climate of the East Coast to the drier climate of Colorado. As sanitariums sprang up throughout the state, Colorado’s reputation as a Wild West frontier gave way to a reputation as a healthy and health-conscious area. However, Colorado’s sanatoriums–including “the San”–stopped taking TB patients in the early 1900s after scientists discovered that the disease was communicable rather than hereditary.

The sanitorium continued to treat non-tuberculosis patients and to develop new treatments and facilities. By 1962, the Sanitorium became Boulder Memorial Hospital and merged its natural remedies with medical departments that utilized the newest technologies. Boulderites today continue in the health-conscious vein of the sanitorium and its successors, taking advantage of both healthcare technology and clean eating, exercise, and alternative therapies to ensure their health is the best it can be.


Switzerland Trail Railroad

The Colorado & Northwestern Railroad route between Boulder and Ward was named “The Switzerland Trail of America”.  It operated until 1919.

Chautauqua Opened

Boulderites approved a $20,000 bond election for the Texas-Chautauqua Auditorium.  Now the Colorado Chautauqua, it hosts lectures, live music, and silent films, and includes the Chautauqua Dining Hall and short-term lodging at the base of the Flatirons. It was designated a National Historic Landmark in 2006.



Foothills Preserved

Boulder’s request for 1,800 acres of mountain backdrop/watershed extending from South Boulder Creek to Sunshine Canyon was approved by Congress.

Tungsten Discovered

Tungsten was discovered in the mountains west of Boulder.  The ore’s value soared, especially when the country’s entry into World War I greatly increased demand. By that time Boulder County was the world’s leading producer of tungsten ore.


Oil Discovered

The Boulder oil field was discovered on what is now the Diagonal Highway near the Airport.  It was the first field in what is now a vast oil & gas producing area, the Denver-Julesburg basin.


Speeding Laws

City ordinance made it “unlawful for any person to ride or drive within Boulder at a rate of speed in excess of 6 miles per hour.”


Carnegie Library

The Carnegie Library was built with money donated by steel tycoon Andrew Carnegie in response to a request from local organizer Clara Savory. Located at 1125 Pine Street, the building was modeled after Greek architecture, reflecting Boulderites’ opinion of their town as the “Athens of the West.” It is now he Carnegie Branch Library for Local History, housing the collections of the Boulder Historical and Genealogical societies.



Anti-Saloon Ordinance

Boulder passed an anti-saloon ordinance, due to a powerful female-led Prohibition Movement. The City did not officially overturn this measure until 1967, although 3.2% beer was legal beginning with the end of Federal Prohibition in 1933.



Ivy Baldwin

Ivy Baldwin made a record-breaking high wire walk on a cable stretched 565 feet high across Eldorado Springs canyon. Now, rock climbers from around the world are drawn to Eldorado Springs, the Flatirons and Boulder Canyon.  Many of the country’s greatest climbers call Boulder home.



Interurban Train

The electric Interurban train made its first run between Boulder and Denver. Its last trip was in 1926. (view of train in Denver)




Boulderado Hotel

The Boulderado Hotel opened for business on New Year’s Day. The city’s first luxury hotel, it is still welcoming guests in an elegant, historic setting.



Miners Strike

3,000 coal miners in Boulder County went on a strike that lasted five years. Fights and other sporadic violence between striking miners and scabs became commonplace requiring patrols by deputies in the Boulder County mining community of Lafayette.


Boulder Canyon Road

The Boulder Canyon Road had been completed in 1871, but it wasn’t until 1911 that the first car, a Stanley Steamer, made the difficult trip up the canyon from Boulder to Nederland. The Steamer replaced the daily stagecoach which had made the 18-mile trip for the previous 40 years.



Street Paving

With the automobile becoming commonplace, the process of paving Boulder’s streets began in September, at the corner of 18th and Pearl. The paving quickly spread down Pearl Street, the commercial center of town. Fifteen-foot-wide concrete sidewalks were also added on either side of the street, replacing the flagstone walkways.



Hellems Hall

Hellems Hall was the first building completed in the “Rural Italian” or “Tuscan” style (sandstone and red roof tile) that now dominates the the University of Colorado campus.


KKK in Boulder

The KKK paraded down Pearl Street. For a few years the Klan played a dark but prominent role in Colorado politics and forced their white supremacy agenda on residents. During that time, the first known African-American female graduate of the University of Colorado, Lucile Berkeley Buchanan Jones was not permitted to walk at her graduation ceremony.


Valmont Power Plant

Construction began on the Lakeside (now Valmont) Power Plant, the “largest industrial project in the history of Boulder County”. In 2017 its conversion from coal to natural gas was completed.

Pool Constructed

Hygienic Swimming Pool (now Spruce Pool) opened using warm water produced from the manufacture of ice at adjacent Hygienic Ice Company.


Folsom Field Completed

The University of Colorado Stadium (Folsom Field) was completed in time for Homecoming. Its 500th game coincided with the Grand Opening of the Museum of Boulder’s permanent exhibit, November 17, 2018.


Streetcar End

Boulder’s electric streetcar service ended, as many residents had acquired personal automobiles and the streetcar was becoming obsolete. Begun in 1901, the streetcars ran the length of Pearl Street, and on to Denver. 


Boulder County Courthouse Fire


Amphitheater Built

As part of the New Deal, the Civilian Conservation Corps finished the Flagstaff Mountain amphitheater, still an attraction for weddings and its stunning views.



Boulder Theater

The Curran Opera House (1906) was renovated and turned into the Boulder Theater. The interior was updated and expanded to make the theater more suitable for movies. Art deco style changes included colorful murals and exterior decoration. The theater became a historic landmark in 1980 and incorporated live music, making it a national attraction and an enduring focus of Boulder’s vibrant entertainment scene.



Boulder High School

The new Works Progress Administration-built Boulder High School was opened. Nude sculptures of “Wisdom and Strength” (Minnie and Jake) over the entrance were allowed to remain despite controversy.



CU All-American

Byron “Whizzer” White, later Rhodes Scholar and U.S. Supreme Court Justice, became CU’s first All-American football player.



The National Bureau of Standards (now known as the National Institute of Standards and Technology) broke ground in Boulder. Boulder citizens raised funds to purchase the site, and the Boulder Chamber of Commerce deeded the land to the federal government. The groundbreaking ceremony was attended by President Dwight Eisenhower, signaling Boulder’s new role as a mecca for federal research facilities and incubator for private-sector technology companies.


Rocky Flats Opened

The Rocky Flats Nuclear Weapons Factory opened eight miles south of Boulder. Initially seen as a boon to the local economy, the site clandestinely manufactured highly radioactive plutonium pits, causing significant environmental contamination and sometimes fatal health impacts to workers. Several large protests were staged in the 1970s and 80s and it was finally closed in 1992. Access to the grounds are regularly litigated given the continuing health hazards.

Denver-Boulder Turnpike

The Denver-Boulder Turnpike (now US 36) was completed and opened to traffic. The highway was the first of its kind in Colorado and preceded the introduction of the Interstate system. It cost 25 cents for a pleasant drive from Denver to Boulder through rolling green farmland. Boulder’s population began to grow, and traffic volume so greatly exceeded expectations that the turnpike fees paid off the $6.3 million in bonds in 15 years. The toll road became a free public road in 1967.

Today, motorists can take a quick trip between Boulder and Denver on U.S. 36, but that wasn’t always the case. Before the Denver-Boulder Turnpike was completed in January 1952, travelers took a long and winding journey east on State Highway 7 and south on U.S. 287 to Federal Boulevard. As early as the 1920s, CU engineering professor Roderick Downing proposed a highway between Denver and Boulder, and his idea was finally adopted by the Colorado Legislature in 1947. The project began on October 16, 1950.

The highway was immediately popular when it opened in 1952, even though motorists had to pay a toll of 10¢ to drive to Broomfield and 25¢ to drive to Denver. About 4,000 cars per day traveled on the Turnpike over the next few months, and by 1967 the state had collected enough tolls to pay off the cost of construction 13 years early.

The Turnpike has impacted our area in many ways: Boulder is more closely connected to Denver, workers and tourists have quicker and easier commutes, cities along the Turnpike have grown substantially, and developments like Interlocken and Flatiron Crossing now contribute to the local economy. While modern commuters may complain about traffic on the Turnpike–it’s certainly more congested now than it was in its early years–there’s no doubt that Boulder and the surrounding area are still reaping its benefits.


Boulder Reservoir

A water bond issue for $2 million was passed to build Boulder Reservoir in the northeast part of town. It was a part of the Colorado-Big Thompson trans-mountain water diversion project.  The “res” is now a popular site for swimming and boating, as well as a water-storage facility.



Colorado Building

Construction began at Boulder’s first “skyscraper,” the 9-story $1 million Colorado Insurance Group building at 14th and Walnut.  Still standing, it remains the tallest building downtown, as a City Charter amendment was passed in 1971 to restrict new construction of downtown buildings to a height of 55 feet.


Old Depot Closed

Railroad passenger service closed to the old depot in downtown Boulder. The Victorian building, built by the Union Pacific Railroad in 1890, was saved by concerned citizens and was relocated to 30th and Pearl Street. Now a historical landmark, the depot was used as an event center until acquired by the city in 2008 and moved to Boulder Junction, near the BNSF railroad tracks.


“Blue Line”

“Blue Line” regulations were passed to prevent future development along mountain backdrop by restricting city water service above 5,750 feet.


New Library

Construction began on the new Boulder Public Library on Canyon after a library bond was passed.



The state of Colorado purchased 565 acres below the Flatirons to turn it over to the federal government for construction of the National Center for Atmospheric Research (a rare exception to Boulder’s “Blue Line”). Designed by architect I. M. Pei, the structure was modeled after Mesa Verde cliff dwellings in southwest Colorado and the sandstone building material was meant to blend into the surrounding landscape. Today NCAR and CU atmospheric scientists collaborate on cutting edge research.


Scott Carpenter Park

Scott Carpenter Park was named in honor of the NASA astronaut from Boulder who was the second man to orbit Earth during the Mercury-Atlas 7 Mission in 1962.


Crossroads Mall

Crossroads Mall (“where good things happen”) was built. 29th Street Mall now occupies the area.



Space Industry

The space industry, led locally by the National Bureau of Standards and Beech Aircraft Corporation had a direct impact on Boulder’s growth. In the previous 13 years, population and employment doubled, while there was a tripling of retail sales and a 400% increase in total assessed valuation of the city.



The IBM plant along the Boulder-Longmont Diagonal was built, triggering growth and cementing Boulder’s place as a high-tech hub.



Prohibition Ends

Boulder voters approved the sale of intoxicating beverages after 60 officially dry years.

Open Space Sales Tax

Boulder voters approved the nation’s first tax to preserve open space in the community. This has prevented urban sprawl and preserved mountain views, but limited the amount of land available for housing. The City’s open space now includes over 45,000 acres of preserved and protected land that includes precious wildlife habitat, distinctive geologic features, and 155 miles of trails.


Celestial Seasonings

Celestial Seasonings, now a worldwide tea company, was founded by Mo Siegel of Boulder. Five years later, the company’s Red Zinger Bicycle Classic first raced through Boulder.


Arguably one of the most recognizable names to come out of Boulder is Mo Siegel and his tea company Celestial Seasonings. When he was a child, Mo picked berries and sold them to neighbors, who used them to make jam. After moving to Boulder in 1969, he put this entrepreneurial spirit to work and started the company at age 19. It grew out of his experience with herbal teas while working at a health food shop in Aspen and his love of hiking and knowledge of local herbs. Mo chose the name Celestial Seasonings after co-founder Lucinda Gates’ nickname in high school – boys called her ‘celestial seasonings’ since they said she looked like she came from heaven.

The first batch of tea was a mix of herbs picked near Boulder Canyon. Mo and the six friends working with him used screen doors to dry the herbs, sold the bales to a local health food store in 1970, and then Mo promptly left to travel South America for the summer. When he came back, he was shocked to discover the blend was wildly popular. In an interview from the Maria Rogers oral history collection at the Carnegie Library for Local History, Mo said he wasn’t surprised that the idea of herbal teas had worked, since it was popular in Europe, only that this “wretched blend” was so well-liked. The following year, Mo’s 24 was the first blend sold under the Celestial Seasonings name, with 16 of the herbs picked in Colorado. The mix was sold in muslin bags that Mo and the small crew who worked with him sewed by hand. The material was dyed a specific shade called “Celestial Red” to help build their brand. In 1972, two of the blends that remain top sellers to this day were released: Red Zinger and Sleepytime. Almost overnight, these teas turned Celestial Seasonings into a household name. Today, it is the largest tea manufacturer in North America, serving 1.6 billion cups of tea worldwide each year.

Even with their success, the company had a rocky journey at times. In 1984, Kraft bought Celestial Seasonings, and Mo retired two years later after overseeing the transition. Lipton was poised to buy the company in 1987, but the merger was stopped after Bigelow challenged the sale under antitrust laws, as Lipton and Celestial Seasonings together made up over 80% of tea sales in the U.S. In 1989, the company was bought back by Celestial Seasonings management with investment from Vestar Capital Partners. Mo returned as CEO in 1991, oversaw the company merge with The Hain Food Group in 2000 to become Hain Celestial Group, and retired again in 2002.

Mo wasn’t just ambitious in tea – after he learned how popular the Tour de France was in Europe, he decided to start a similar bike race in the U.S., and the Red Zinger Bicycle Classic was born. The first race in 1975 had a purse of $10,000, ten times the previous largest prize in the U.S, and attracted seventy of the top bikers. Celestial Seasonings ran the race for five years before selling it since it required too much money and manpower from the company to run it.

Counterculture Turmoil

The counterculture turmoil of the Sixties came to Boulder; Central Park was declared a health hazard because of transients. Progressive views begin to dominate the Boulder political scene.


Population Boom

The City’s population reached almost 67,000, having tripled since 1950.

Anti-War Demonstrations

CU’s Regent’s Hall was occupied by youthful anti-war demonstrators.


Vietnam War Protests

The turnpike interchange at 28th Street was occupied by demonstrators protesting the Vietnam War.

Central School Demolished

The demolition of Central School stimulated the creation of Historic Boulder, Inc. and the adoption of a City Landmark Ordinance.


Penfield Tate II

Penfield Tate II was elected Boulder’s first black mayor. To this day, he remains the only African-American to serve as a Mayor in Boulder County.

Boulder’s Bombings

Boulder’s bombings. Six Chicano activists (known as Los Seis de Boulder) were killed in two separate bombings. These crimes have never been solved and some believe they were perpetrated by the FBI. 

On May 27th, 1974 a bomb went off at the Chautauqua Auditorium, killing three people. Two days later a second bomb went off at a Burger King on 28th Street, killing three more people and severely injuring an additional person. The victims ranged in ages from 20-31 and were all associated with the Chicano Movement at the University of Colorado at Boulder.

Originally a negative word, Chicano was used to describe people of Mexican descent. In the 1960s the word Chicano was repurposed and the Chicano movement began to gain prominence. The movement was particularly active in the Southwest region of the US including in Boulder. Chicano enrollment at CU swelled, growing from just 50 in 1968 to 1,500 in 1972. Many of those students took issue with the way they were treated at CU and in 1974 they were left waiting for months for financial aid checks. Before the bombs Chicano students took over a building on campus for 3 weeks as part of a protest.

Because all of the bomb victims were associated with the Chicano movement there was a feeling amongst many of those in the Chicano movement that the bombs were perpetrated by the government. The suspicion fell in particular on the FBI who had been called to help with the case. The FBI program called COINTELPRO (Counterintelligence Program) was active in the 1970s and was known for That program surveilling and infiltrating civil rights groups such as Black Panthers, American Indian Movement, Weathermen, Puerto Rican Independence Movement. The program even surveilled Martin Luther King.

The official finding of the Boulder police department is that both bombs were accidentally detonated by the victims. They believe that the bombs were supposed to be placed in various locations to make a statement perhaps in conjunction with the other Chicano protests. The FBI files on the case were lost in a Kansas City fire, which further confirmed some people’s theory of FBI involvement. The case remains unsolved to this day.

There is now a sculpture honoring Los Seis by CU student Jasmine Baetz. It is unclear if it will be a permanent memorial but it is currently in a small green space in front of Temporary Building 1, next to Sewall Hall on the CU Boulder campus.

The Victims-
Reyes Martinez (26) who was an attorney who graduated from CU
Neva Romero (21) who was a junior at CU
Una Jaakola (24) who was a graduate of CU
Florence Granado (31) who had attended CU
Heriberto Teran (24) who was a former CU student
Francisco Dougherty (20) who was studying pre-med at CU
Antonio Alcantar was injured in the bomb, he lost a leg


Same Sex Marriage

Boulder County Clerk Clela Rorex issued the first same sex marriage licenses in the United States in response to a marriage application from two men.


In 2018, the Boulder County Courthouse was added to the National Register of Historic Places in recognition of its significance to state and federal LGBTQ history and civil rights struggles.


Pearl Street Pedestrian Mall

A four-block downtown stretch of Pearl Street was closed to automobile traffic and the pedestrian mall opened. With Boulder’s population explosion in the 60s and 70s, the downtown area was losing market share to shopping centers outside the city center. The mall revitalized downtown Boulder and is one of the most successful pedestrian malls in the country.

Danish Plan

Boulder voters approved a 2% growth limitation referendum, known as the Danish Plan. Slowed growth within the City limits has followed, but population in nearby towns has grown rapidly. 



Bolder Boulder

Seven years after Boulder’s Frank Shorter won the Olympic marathon, the Bolder Boulder was run for the first time on Memorial Day through the streets of Boulder, a city that loves to run. Its finish was moved to Folsom Field on the CU campus in 1981. This helped facilitate the growth of the event, and today over 50,000 people participate in one of the premier 10k races in the country.



Farmer’s Market

A group of local farmers decided to organize a farmer’s market to support small farmers. They secured a permit from the city and set up in Central Park. The market continued to grow and today it is a popular community event that helps promote local agriculture.


Nobel Prize

Tom Cech, a CU professor, and Sidney Altman, a CU graduate, received the Nobel Prize in Chemistry. Scientists with Boulder ties go on to earn four more Nobels in the next two decades.


JonBenet Ramsey

The unsolved Christmas murder of six-year-old JonBenet Ramsey brought shock, grief and notoriety to Boulder.


Dushanbe Tea House

The Dushanbe Tea House was erected on 13th Street. Beginning in 1987, forty artisans from the Sister City of Dushanbe, Tajikistan constructed the exquisite building in traditional style. It was then disassembled and shipped to Boulder for reconstruction.



Boulder hosted its 150th anniversary celebration.


Labor Day Wildfire

On Labor Day a wildfire broke out in Four Mile Canyon northwest of Boulder. A dry August and high winds created conditions ideal for the fire which ripped through the canyon. Six thousand acres were ablaze by the end of the day, forcing the evacuation of 3,000 residents. Firemen contained the blaze a week later but not before 169 homes were destroyed, making it the most destructive fire in Colorado history at the time.


1000-Year Flood

A slow-moving September cold front stalled over Boulder, where it mixed with warm humid monsoonal air. Heavy rain and catastrophic flooding occur, with a week’s rainfall totals that are comparable to the average annual precipitation.  Four are killed in Boulder and property damage is extensive in what was termed a once-in-1000 years event.


The Museum of Boulder moved to its new downtown location.

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