The California Oil Museum at 1001 E. Main Street, Santa Paula (corner of Main and 10th) is the birthplace of Union Oil Company (now part of Chevron). The building was completed on October 17, 1890 and originally was the Santa Paula Hardware Company Building, housing the headquarters of the Union Oil Company on the 2nd floor. Union Oil moved its headquarters to Los Angeles in 1900, but continued to operate a field office out of this building.

The Union Oil Museum was established in 1950. The building was restored to its original appearance for its centennial celebration in 1990. The building is also a California Historical Landmark and is listed on the National Register of Historic Places.