Fort Yuma was a fort in California located in Imperial County, across the Colorado River from Yuma, Arizona. It was Established in 1848. It served as a stop on the Butterfield Overland Mail route from 1858 until 1861. The fort was retired from active military service on May 16, 1883, and transferred to the Department of the Interior. The Fort Yuma Indian School and the Saint Thomas Yuma Indian Mission now occupy the site. It is one of the "associated sites" listed as Yuma Crossing and Associated Sites on the National Register of Historic Places in the Yuma Crossing National Heritage Area. In addition, it is registered as California Historical Landmark #806.

Imperial County is a county located on the southeast border of the U.S. state of California. As of the 2020 census, the population was 179,702, making it the least populous county in Southern California. The county seat and largest city is El Centro. Imperial is the most recent California county to be established, as it was created in 1907 out of portions of San Diego County.