Colorado County Evolution

The following maps trace Colorado from just before the Colorado Territory was created through today, showing the evolution of the county borders.

Before Colorado Territory, 1860-1861

Original 17 Counties, 1861-1866

Colorado Territory was established by Congress on February 28, 1861. The first Legislative Assembly of the Territory of Colorado convened on September 9, 1861. They quickly enacted laws establishing the seventeen original counties. At that time Conejos County was called Guadalupe County, but within a couple years had become known by its current name.

1866, Saguache and Las Animas Counties added

1870, Greenwood County created, other county lines redrawn

The creation of Greenwood county to finally cover the Cheyenne Reservation also brought with it several other changes. Greenwood took part of Huerfano county, and Pueblo also took a bit of Huerfano county. Huerfano county took the southern half of Fremont county as a consolation for losing so much of the eastern part of the state.

1872, Platte County created

1874, 2 Counties removed, 6 Counties created

In 1874, Greenwood and Platte Counties were abolished, Bent, La Plata, Hinsdale, Rio Grande, Elbert, and Grand Counties were created. (Bent County is often reported to have been created in 1870, but this page creator believes that those reports are using the date of the creation of the now defunct Greenwood County as the date of the creation of the successor county.)

1876, Colorado becomes a State, San Juan County created

Colorado was admitted as the 38th state of the Union on August 1, 1876.

1877, Gunnison, Routt, Custer, and Ouray Counties created

1879, Chaffee County created

1881, Dolores and Pitkin Counties created

1883, 6 Counties created

In 1883, Garfield, Eagle, Mesa, Delta, Montrose, and San Miguel Counties were created.

1885, Archuleta County created

1887, Logan and Washington Counties created

1889, 13 Counties created

In 1889 the legislature was very busy. The following counties were created: Montezuma, Rio Blanco, Morgan, Sedgwick, Phillips, Yuma, Lincoln, Kit Carson, Cheyenne, Kiowa, Prowers, Otero, and Baca.

1893, Mineral County created

1899, Teller County created

1902, Arapahoe County split up

The Arapahoe county split created Denver and Adams Counties, and sent parts of what had been Arapahoe County to Washington and Yuma Counties. Due to some legal wrangling some of the final results of this act were not officially in place until 1906.

1908, Park gets a piece of Jefferson County

1909, Jackson County created

1911, Crowley and Moffat Counties created

1913, Alamosa County created

The Present

A proposal on the November, 1998 ballot to make the town of Broomfield into the city and county of Broomfield was voted on by the people of Colorado - it passed. This created, effective 2001, a small county (much smaller than Denver) that covers the corners of what were Jefferson, Boulder, Weld, and Adams Counties. The map now looks like: