From the plaque:
In October 1780, Father Francisco
Garcés and companions began Mission La Purísima
Concepción. The mission/pueblo site was inadequately
supported. Colonists ignored Indian rights, usurped the
best lands, and destroyed Indian crops. Completely frustrated
and disappointed, the Quechans (Yumas) and their allies
destroyed Concepción on July 17-19, 1781.
Plaque placed by the State Department of Parks and Recreation in cooperation with the Quechan Tribal Council, the Catholic Archdiocese of San Diego, Imperial Valley Pioneers and Squibob Chapter, E Clampus VItus, October 9, 1982.