Davis County is a county located in the U.S. state of Utah. As of the 2010 census, the population was 306,479, making it the third-most populous county in Utah. Its county seat is Farmington, and its largest city is Layton. The county was created in 1850 and was named for Daniel C. Davis, captain in the Mormon Battalion.Davis County is part of the Ogden-Clearfield, UT Metropolitan Statistical Area as well as the Salt Lake City-Provo-Orem, UT Combined Statistical Area.