Arapahoe County, Colorado

county in Colorado, United States

Arapahoe County (/əˈræpəh/ ə-RAP-ə-hoh) is a county in the state of Colorado in the United States. As of the 2010 census, 572,003 people lived there. That made it the third-most populous county in Colorado. The county seat is Littleton. The most populous city is Aurora.