Round Valley Regional Preserve was once home to California Indians and probably lay on the boundary between several tribal groups, where people from East Bay and San Joaquin Valley groups met periodically to trade and socialize, and evidence of Native American use has been found at several sites there. In 1873 Thomas Murphy, an Irish immigrant, bought the land and established a ranching and farming operation. His grandson Jim Murphy sold the core 700 acres of Round Valley to the East Bay Regional Park District in 1988 so it could be preserved as open space for public enjoyment instead of being used for residential development or as a refuse disposal site. The 2191-acre preserve contains grassland, oak woodland and savannah, shrubland, and riparian woodland plant communities, with Round Valley Creek supporting riparian and wetland vegetation. It provides habitat for a wide variety of wildlife, including the endangered San Joaquin kit fox at one of the northern limits of its range in California, nesting golden eagles, burrowing owls, California red-legged frogs, western toads, western pond turtles, and Pacific tree frogs. Its bedrock is Cretaceous Panoche shale and sandstone with recent alluvium on the surface in valleys and creek drainages, and the Marsh Creek (Mount Diablo) Fault lies about two miles southwest of the preserve.