Agua Mansa is designated California Historical Landmark (No. 121). The marker is located at Agua Mansa Pioneer Cemetery. The first burial occurred in 1852, and the last occurred 111 years later in 1963. In 1967, the cemetery became a branch of the San Bernardino County Museum after its acquisition by San Bernardino County. It has a museum and chapel, and tours are available.
Records of who is buried in the cemetery are incomplete but about 750 names have been identified out of a total of 2,000 estimated burials. Only a few grave markers remain today. The earliest known interment was that of Louis Robidoux, who came to California in 1844 and bought the Jurupa Rancho near today’s City of Riverside. Another burial was that of Cornelius Jensen in 1886; Jensen was a Danish sea captain who established a store at Agua Mansa before moving to part of the Robidoux ranch. Jensen’s wife, Mercedes Alvarado, is also buried in the cemetery along with other members of her family. Lorenzo Trujillo, the original patriarch of the community, is also believed to rest somewhere in a grave that long ago lost its marker.