Spanish colonial missions and Mexican rancho and pueblo adobe structures are among California's earliest existing structures and the only above-ground remains of the state's original settlement by the Spanish and Mexican people. The Northridge earthquake of January 17, 1994, resulted in tragic losses to a number of these historic adobe buildings. The earthquake also provided a rare opportunity to assess the damage that can occur to such structures as the result of a large earthquake. The intent of this study—part of the GCI's long-term commitment to researching conservation measures appropriate for historic adobe structures—was to survey the damage to buildings and make an informed evaluation of their seismic performance. The ultimate goal was to use the lessons learned from the Northridge earthquake and the results of retrofit research to help owners, building officials, cultural resource managers, architects, and engineers to understand the risks earthquakes pose to historic adobe buildings and the necessity for taking considered action to limit those risks.