Colorado County Evolution
This page created by
Don Stanwyck for the
Copyright 2003, Don Stanwyck and the CoGenWeb Project.
All Rights Reserved.
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
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
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: