Salt Lake County is located in the U.S. state of Utah. As of the 2020 United States census, the population was 1,185,238, making it the most populous county in Utah. Its county seat and largest city is Salt Lake City, the state capital. The county was created in 1850. Salt Lake County is the 37th most populated county in the United States and is one of four counties in the Rocky Mountains to make it into the top 100.