Las Animas County.
Colorado's largest county is the city and county of Denver (which is also the largest city in the state) and the 2009 population was 610, 345
The largest county and city in both size and population is Denver
Las Animas County in Southern Colorado. The county seat is Trinidad.
The Denver County (and also the city)
Las Aniimas County has the largest area and the City and County of Denver has the greatest population.
Denver: 598,707 Colorado Spring: 360,890 Aurora: 276,393
Las Animas County is the largest county in the state of Colorado. 4,775 square miles (12,368 km²)
Denver County, El Paso County, Arapahoe County, and Jefferson County.
In terms of population the 4 largest counties in Colorado are:El Paso - 622,263Denver - 600,158Arapahoe - 572,003Jefferson - 534,543In terms square miles it is:Las Animas - 4,773Moffat - 4,743Weld - 3,987Mesa - 3,329
Las Animas County at 4,775 square miles.
Las Animas County at 4,773.27 square miles. Almost four Rhode Islands can be fitted into Las Animas County.
Centennial is located in Arapahoe County and is part of the Denver-Aurora metropolitan area. It is the states 10th largest city. Arapahoe County calls itself "Colorado's First County" since its origins predate the Pike's Peak Gold Rush.