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. Salt Lake County has been the only county of the first class in Utah – under the Utah Code is a county with a population of 700,000 or greater. Although, Utah County directly to the south has recently reached this threshold.

The Jordan River is a 51.4-mile-long (82.7 km) river in the U.S. state of Utah. Regulated by pumps at its headwaters at Utah Lake, it flows northward through the Salt Lake Valley and empties into the Great Salt Lake. Four of Utah's six largest cities border the river: Salt Lake City, West Valley City, West Jordan, and Sandy. More than a million people live in the Jordan Subbasin, part of the Jordan River watershed that lies within Salt Lake and Utah counties. During the Pleistocene, the area was part of Lake Bonneville.