The Pacific Coast Railway Co. builds the pier for commercial shipping. Union Oil Co. of California (later Unocal) leases the new pier, expanding its operations. 

The last oil is shipped off of neighboring Harford Pier. All oil out of San Luis Bay is now shipped off the Pacific Coast Railway Co. Pier.

With the Southern Pacific Railroad and the Great Depression as factors, use of the Pacific Coast Railway Co. and the piers declined. The oil transportation facility was abandoned and the a portion of the Harford pier was demolished to aid navigation in the bay.

Union Oil buys the Pacific Coast Railway Co. Pier and changes the name to Union Oil Pier. The pier plays an important role in supplying the U.S. Pacific Naval Fleet with fuel during World War II.

Along with the Harford and Avila Piers, the Union Oil Pier is now managed by the Port San Luis Harbor District.

Unocal replaces the wooden pier destroyed in a recent storm with a steel and concrete pier. The pier now extends six-tenths of a mile into the bay and is constructed in the same footprint as the original pier.