Jefferson County, Colorado Overview -On November 1, 1861, Jefferson County became one of the original 17 counties of Colorado, named after its namesake of the Jefferson Territory, Thomas Jefferson, author of the Declaration of Independence and the third U.S. President. -Commonly called “Jeffco” -The fourth most populous county in Colorado with a population of 534,543 according to the 2010 census. -Jeffco encompasses 744 square miles
-County slogan is “Gateway to the Rocky Mountains”. -Golden is the county seat. -Home to Jefferson County School District R-1 (Jeffco School District). -The Federal Correctional Institution is in Englewood, which is in unincorporated Jefferson County. -In 1952-1989, the Rocky Flats Plant produced nuclear weapons in Jefferson County. -Major employers in Jefferson County include Coors Brewing Company and Colorado School of the Mines, both located in Golden. -Jefferson County cities, towns and unincorporated communities include: Arvada (part), Edgewater, Golden. Lakewood, Littleton (part), Westminster (part), Wheat Ridge, Bow Mar, Lakeside, Morrison, Mountain View, Superior (part), Buffalo Creek, Conifer, Evergreen, Foxton, Idlesdale, Pine, Pine Junction