History & Demographics
Assay office museum

History & Demographics of Boulder County

Boulder County was one of the original 17 counties organized by an enabling act of the first Colorado Territorial Legislature on Nov. 1, 1861. The county is home to approximately 323,000 residents and includes some of the most diverse, natural landscapes and sustainable development along the Front Range. The county seat resides in the City of Boulder.

Geography & Demographics

Boulder County is an exciting, special and spectacular 742 square miles. Located in north central Colorado, it almost forms a rectangle except for its western boundary that is the continental Divide. The bordering counties are Larimer on the north, Weld and Broomfield on the east, Jefferson and Gilpin on the south, and Grand on the west.

Eastern Boulder County begins in the High Plains, at just under 5,000 feet above sea level, and climbs through the foothills, montane, sub-alpine and alpine ecosystems to Longs Peak at 14,259 feet. The 9,000-foot change in elevation represents climatic and environmental differences, as well as a vast array of plants, wildlife and recreational opportunities.

The plains are part of what the explorer Stephen Long erroneously labeled the Great American Desert. It is here that many of Boulder County’s towns and cities are located – Longmont, Erie, Lafayette, Louisville, and Superior. Some of the resources found in the plains are rich, irrigated farmlands and rolling pastures, lignite coal, iron ore and small amounts of oil and gas. The land is accented with lakes and ditches which are used mainly for agricultural purposes, the result of human effort to convert the dry soil into productive land.

To the west of the plains are the foothills. Nestled in the valleys against the first, prominent rock formations are Lyons, Boulder and Eldorado Springs. You can see the red rock fountain formation rising above the plains. This area is the source for construction stone, some of it used to build the University of Colorado.

Twisting between and around the rapidly ascending rock formations are the canyons, which serve as gateways to the mountains. They are also the drainage ways, which bring the waters of the North and South St. Vrain, Left Hand, North and South Boulder creeks to the plains. As the terrain rises, you can see signs of Boulder County’s mining towns and history. Of these, a few have survived as communities (such as Gold Hill and Eldora), but only Jamestown, Ward and Nederland are incorporated towns.

The area west of the Peak to Peak Highway is largely owned by the federal government and managed by the U.S. Forest Service and the National Park Service. This area extends to the Continental Divide, which forms the western boundary of Boulder County. Boulder County contains major portions of Rocky Mountain National Park, Indian Peaks Wilderness and Roosevelt National Forest.

From dry land wheat farms to alpine tundra, from urban parks to wilderness, from “high-tech” recreation centers to historic landmarks, Boulder County is a wonderful conglomeration of nature’s gifts and human handiwork.


The estimated population of Boulder County for 2017 is just over 323,000.

*Includes towns of Erie, Jamestown, Lyons, Nederland, Superior and Ward, and unincorporated areas such as the communities of Allenspark, Eldorado Springs, Gunbarrel and Niwot.

History – County & Courthouse

  • 1803: Thanks to the Louisiana Purchase, territory within what is now Boulder County becomes part of the United States
  • 1858: Gold was discovered in Dry Creek, stimulating the Pikes Peak Gold Rush
  • 1859: Coal was discovered in the Marshall area southeast of Boulder; The first record of modern settlement in Boulder County
  • 1861: The Colorado Territory was created
    • Boulder one of 17 counties represented in the first Territorial Assembly
    • Native Americans were the first inhabitants of the county
    • Followed by settlers, gold miners, farmers, coal miners and traders
  • 1866: Boulder County’s first newspaper, the Valmont Bulletin, began publication (later renamed the Boulder Valley News)
  • 1869: The first Boulder County Fair took place; The Boulder County Agricultural Society was founded
  • 1873: The first railroad was extended to Boulder County
  • 1882: Cornerstone of the original Boulder County Courthouse was laid
    • Building marked the official designation of a public square
    • Meeting place of the Boulder County Commissioners
    • Original structure was considered elaborate for a small pioneer town
  • 1890: The Boulder Daily Camera was founded
  • 1894: The Great Boulder Flood
  • 1898: The Chautauqua Auditorium was opened on July 4th
  • 1910: The Boulder County coal miners’ strike
  • 1932: The original courthouse and many records were destroyed by fire
  • 1934: New courthouse built on the same site
  • 1962: Two wings were added to the courthouse complex
  • 1970: The Boulder County Comprehensive Plan was adopted
  • 1973: Boulder County’s first open space land was purchased
  • 1976: Voters approved the Danish Plan, a 2% growth limitation referendum
  • 1986: The Lafayette-Louisville Downtown Revitalization Partnership was established
  • 1993: The Boulder County Historic Preservation Ordinance was adopted

Contact Us

Administrative Services

303-441-4524 (fax)


Information Desk / Main Lobby
Downtown Historic Courthouse
1325 Pearl Street
Boulder, CO 80302
Map & Directions
Hours: 8 a.m. – 4:30 p.m. M-F

Mailing Address

Boulder County
PO Box 471
Boulder, CO 80306