Jefferson Territory - Counties

Counties

On November 28, 1859, the Territory of Jefferson created 12 counties:

1. Cheyenne County evolved into Laramie County, Wyoming
2. St. Vrain County evolved into Weld County, Colorado
3. Arrappahoe County evolved into Arapahoe County, Adams County, and the City and County of Denver, Colorado
4. El Paso County evolved into El Paso County and Pueblo County, Colorado
5. Fountain County encompassed most of southeastern Colorado
6. Park County evolved into Park County, Colorado
7. Saratoga County evolved into Grand County and Summit County, Colorado
8. North County evolved into Jackson County, Colorado
9. Jefferson County evolved into Jefferson County, Colorado
10. Jackson County evolved into Boulder County, Colorado
11. Heele County evolved into Larimer County, Colorado
12. Mountain County evolved into Gilpin County and Clear Creek County, Colorado