Union Oil Company Building, Historic building and oil museum in Santa Paula, California, United States.

The Union Oil Company Building, also known as the Santa Paula Hardware Company Building, is a two-story structure in Santa Paula, California. Originally, the Santa Paula Hardware and Post Office occupied the ground floor, while Union Oil Company offices were upstairs. The building now houses the California Oil Museum, featuring exhibits such as an 1890s iron and timber drilling rig and a recreated 1890s Union Oil corporate office.

The Santa Paula Hardware Company Building became the birthplace of the Union Oil Company on October 17, 1890, with company offices upstairs and a hardware store and post office below. After the headquarters moved to Los Angeles in 1900, the building remained a field division office. Ventura County designated it Landmark #36 in December 1977, and it is also California Historical Landmark #996 and listed on the National Register of Historic Places.

The California Oil Museum inside displays drilling equipment and gas pumps that show how oil work looked in earlier times. These objects tell the story of workers and engineers who shaped the industry over a century ago.

The building sits at a central intersection in Santa Paula and is easy to reach on foot. Visitors will find museum exhibits displayed throughout the interior alongside restored historic spaces.

The ground floor once held a hardware store and post office while oil company executives ran operations upstairs. This mixing of retail shops with business headquarters reveals how small towns organized their economic centers.