Known as Santa Rosa De Las Lajas (Flat Rocks), this site was used on March 8, 1774 by the Anza exploring expedition, opening the land route from Sonora, Mexico, to Alta California. On December 11 to 15, 1775 the three divisions of Anza's colonizing expedition used this first good watering spot beyond the Colorado River on the way from Sonora to San Francisco.

Marker is on Interstate 8 at milepost 31.3, on the right when traveling east.

Courtesy hmdb.org

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