Boulder County is one of the 64 counties of the U.S. state of Colorado of the United States. As of the 2010 census, the population was 294,567. The most populous municipality in the county and the county seat is Boulder.Boulder County comprises the Boulder, CO Metropolitan Statistical Area, which is included in the Denver-Aurora, CO Combined Statistical Area.HistoryBoulder County was one of the original 17 counties created by the Territory of Colorado on November 1, 1861. The county was named for Boulder City and Boulder Creek, so named because of the abundance of boulders in the area. Boulder County retains essentially the same borders as in 1861, although a 27.5sqmi of its southeastern corner and its approximate population of 40,000 became part of the City and County of Broomfield in 2001.GeographyAccording to the U.S. Census Bureau, the county has a total area of, of which is land and (1.9%) is water.Adjacent countiesLarimer County, Colorado – northWeld County, Colorado – eastCity and County of Broomfield, Colorado – southeastJefferson County, Colorado – southGilpin County, Colorado – southGrand County, Colorado – west
