A major earthquake was reported near Yuma, Arizona, in November 1852. Because of the sparse population and frontier conditions in this region at that time, reports of the earthquake were incomplete and partially inaccurate. Subsequent accounts in historic earthquake catalogs repeated erroneous reports on the data, location, and intensity of the Fort Yuma earthquake. Review of original earthquake accounts indicates that the Fort Yuma earthquake occurred about noon on November 29, 1852. Analysis of the regional geology suggests that the earthquake would have been associated with the seismically active Salton Trough. Comparison of effects of the Fort Yuma earthquake with those of subsequent large earthquakes in the region indicates that the event probably was located about 25 to 50 miles southwest of Yuma and had a probable magnitude of 6 to 7.