Colorado County Map: All 64 Counties

Lake County (seat: Leadville) sits entirely above 9,000 feet in the upper Arkansas River valley and contains Mount Elbert (14,440 ft), the highest peak in the Rocky Mountains. County road departments must maintain high-altitude passes under severe winter blizzard conditions.

In western resort counties such as Pitkin (Aspen), Eagle (Vail), and Summit (Breckenridge), county governments face extraordinary land-use and housing affordability pressures, using transfer taxes and open-space preservation trusts to protect alpine watersheds.

Conversely, Eastern Plains agricultural counties like Weld, Yuma, and Kit Carson cover thousands of square miles of dryland winter wheat, cattle feedlots, and oil and gas extraction fields along the Denver-Julesburg Basin.

During the 1990s technology boom along US Highway 36, the City of Broomfield expanded rapidly across four separate county borders: Boulder, Adams, Jefferson, and Weld. Residents faced four different sales tax rates, four different county courthouses, and conflicting building codes.

To resolve this administrative nightmare, Broomfield voters and the Colorado General Assembly initiated a state constitutional amendment. On November 15, 2001, the City and County of Broomfield was established as Colorado’s 64th county and second consolidated city-county.