Placer County ( PLASS-ərr; Spanish for "sand deposit"), officially the County of Placer, is a county in the U.S. state of California. As of the 2010 census, the population was 348,432. The county seat is Auburn.Placer County is included in the Greater Sacramento metropolitan area. It is in both the Sacramento Valley and Sierra Nevada regions, in what is known as the Gold Country. The county stretches roughly 65 miles from Sacramento's suburbs at Roseville to the Nevada border and the shore of Lake Tahoe.

Squaw Valley (also known as Olympic Valley) is an unincorporated community located in Placer County, California northwest of Tahoe City along California State Highway 89 on the banks of the Truckee River near Lake Tahoe. It is home to Palisades Tahoe (formerly Squaw Valley Ski Resort), the site of the 1960 Winter Olympics. Olympic Valley is the smallest resort area to host the Olympic Winter Games.

Nevada County is a county in the Sierra Nevada of the U.S. state of California. As of the 2010 census, the population was 98,764. The county seat is Nevada City. Nevada County comprises the Truckee-Grass Valley, CA Micropolitan Statistical Area, which is also included in the Sacramento-Roseville, CA Combined Statistical Area, part of the Mother Lode Country.

Nevada City (originally, Ustumah, a Nisenan village; later, Nevada, Deer Creek Dry Diggins, and Caldwell's Upper Store) is the county seat of Nevada County, California, United States, 60 miles (97 km) northeast of Sacramento, 84 miles (135 km) southwest of Reno and 147 miles (237 km) northeast of San Francisco. The population was 3,068 as of the 2010 Census.