In the grassy hills of the western San Joaquin Valley, near Pacheco Pass, San Luis Reservoir is noted for boating, board sailing, camping and picnicking. But it is anglers who find the area's 3 lakes most inviting. Constructed as a storage reservoir for the Federal Central Valley Project and the California State Water Project, it stores runoff water from the delta that would otherwise flow into the ocean. A visitor center at the Romero Overlook provides full information of the reservoirs in the park and telescopes for viewing the area. Once home to the Yokut until they were taken to missions around 1805 where their numbers were decimated by an epidemic (possibly malaria) in 1833. Survivors were killed or run off by Euro American settlers in the 1850s.

The park is on Hwy 152, 7 miles west of I-5, or 33 miles east of Hwy 101 from Gilroy. The park is open all year.