Launch of reinforced-concrete tanker SS Cuyamaca at San Diego Bay, June 12, 1920. (Photo courtesy of the San Diego History Center, AC030 Collection)

In the aftermath of World War I, the United States faced an unexpected industrial problem: steel for shipbuilding had become scarce after years of wartime demand. To keep merchant ships moving, the federal government turned to an unlikely alternative — reinforced concrete.

The effort was overseen by the United States Shipping Board Emergency Fleet Corp., created during World War I to expand the nation’s merchant fleet rapidly. Engineers began experimenting with concrete-hulled cargo vessels using reinforced steel bars embedded in thick concrete hulls — an approach designed to combine concrete’s compressive strength with steel’s ability to resist tension.

Concrete was mixed on the site at ground level, carried aloft in bottom dump buckets that were placed on a centerline dolly, and discharged into hoppers for further distribution by chutes. (Photos courtesy of the San Diego History Center, AC030 Collection). More building can be seen in the photo below.

The result was one of the most unusual shipbuilding experiments in American maritime history.

Big Launch

Among the vessels produced were two ships built in San Diego, launched from a shipyard along San Diego Bay near Point Loma.

On June 12, 1920, thousands gathered along the waterfront to watch the launching of the SS Cuyamaca, a 7,500-ton reinforced-concrete oil tanker constructed by the Pacific Marine Construction Company. Unlike many ships that slide bow-first into the water, the massive hull was launched broadside into San Diego Harbor, creating a dramatic moment as the concrete vessel splashed into the bay.

Miss Lucile Wilde christened the steamer SS Cuyamaca on June 12, 1920. (Photo courtesy of the San Diego History Center, AC030 Collection)

Her sister ship, SS San Pasqual, was built at the same San Diego shipyard just weeks later, completing the city’s only pair of concrete vessels. The two ships together marked a unique chapter in San Diego’s maritime history, demonstrating the experimental concrete shipbuilding efforts of the post‑World War I era.

The SS Cuyamaca was a substantial ship by the standards of the day — about 434 feet long with a beam of 54 feet and a deadweight capacity of roughly 7,500 tons. Though made largely of concrete, its structure relied on steel reinforcement throughout the hull, allowing it to withstand the stresses of ocean travel.

Too Late

Despite the urgency that prompted their construction, the ships arrived too late to play any role in the war. World War I had already ended with the Armistice of 11 November 1918 by the time the vessels were completed.

Side-launch of the SS Cuyamaca at 6:25 p.m. on June 12, 1920. (Photo courtesy of the San Diego History Center, AC030 Collection)

Instead, the SS Cuyamaca entered commercial service. The tanker was chartered by the Franco-Canada Oil Transport Company of New York and began hauling petroleum between Gulf Coast ports. By late 1920, the ship had transited the Panama Canal and was operating between Tampico, Mexico, and ports such as Baton Rouge and New Orleans.

Seaworthy, Inefficicient

Concrete ships proved seaworthy, but they were not particularly efficient. Their hulls were heavier than steel ships of comparable size, and they were slower and more costly to operate. As steel shipbuilding resumed after the war, the concrete fleet quickly lost its economic advantage.

Launch of the concrete ship SS Cuyamaca (San Diego). (Photo courtesy of the San Diego History Center, AC030 Collection)

Other Uses

By February 1924, the Cuyamaca had been converted into an oil barge in New Orleans — a common fate for concrete vessels whose engines were removed and whose hulls were used for stationary storage or transport. The ship was ultimately scrapped in 1926 after only a few years of service.

Other concrete vessels from the same wartime program found unusual second lives. One of the most famous was the SS Palo Alto, which was later towed to Seacliff Beach near Santa Cruz and turned into a seaside amusement pier.

Though the concrete ship experiment was short-lived, the launch of the Cuyamaca and San Pasqual remains one of San Diego’s more unusual maritime moments — a time when wartime necessity pushed engineers to build ocean-going ships out of cement and steel.

 The fleet destroyer repair base, as it appeared in 1928, showing the buildings of the former concrete shipbuilding yard. 32nd Street approaches diagonally from the upper middle right-hand edge. (Photo courtesy of the San Diego History Center, AC030 Collection)

However, for at least one day in 1920, along the shores of San Diego Bay, Point Loma witnessed something few places in the world ever did: the launch of a massive ship made largely of concrete.

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Sources:

Robert Eberhardt, “Concrete Shipbuilding in San Diego, 1918–1920,” Journal of San Diego History, Spring 1995.
San Diego History Center archival collections (Pacific Marine Construction Company records).
Naval History and Heritage Command photographic archives.
ConcreteShips.org historical vessel database.