Summit County, Utah a county located in the U.S. state of Utah, occupying a rugged and mountainous area. As of the 2010 census, the population was 36,324. Its county seat is Coalville, and the largest city is Park City. The county was created in 1854 and later organized in 1861. It is so named because it includes 39 of the highest mountain peaks in Utah. The county's mean elevation is 8,388 feet (2,557 m) above sea level, which is the second-highest of any county outside Colorado. See also Scouting in Utah.