RMS Queen Mary was conceived during fierce competition among European shipping lines for prestige and passengers on the North Atlantic. Cunard ordered the liner in 1929 from John Brown & Company at Clydebank, but the Great Depression halted work in 1931. A British government loan enabled construction to resume on condition that Cunard merge with White Star. Launched in 1934 by Queen Mary, the ship embodied public investment, industrial employment, and national hopes that Britain could match France's Normandie and other modern liners.

Queen Mary entered service in May 1936 on the Southampton–Cherbourg–New York route. More than a thousand feet long, powered by steam turbines, and staffed by a large crew, she carried passengers in sharply differentiated classes. Art Deco interiors combined modern materials with restrained British luxury. In August 1936 she captured the Blue Riband for fastest average Atlantic crossing, lost it to Normandie, and regained it in 1938. Speed was commercial advertising, but safe operation also depended on engineers, stewards, radio officers, dockworkers, and navigators.

At the outbreak of the Second World War, the liner was converted to a troopship, painted gray, and stripped or protected for military service. Known as the “Grey Ghost,” she transported Allied personnel across oceans at speeds that helped evade submarines. In 1942 Queen Mary accidentally struck the escort cruiser HMS Curacoa, which sank with heavy loss of life; wartime orders required the troopship to continue. On a 1943 voyage she carried more than 16,600 people, an enduring record for a single vessel.

After wartime service, Queen Mary carried war brides and returned to civilian use following refit. Together with Queen Elizabeth she sustained a weekly express service and became a symbol of postwar transatlantic travel. Celebrities, migrants, business travelers, and tourists shared the ship unequally according to ticket class and work role. By the late 1950s, jet aircraft crossed the ocean faster and more cheaply. Rising labor and fuel costs made the aging liner unprofitable, and Cunard retired her in 1967 after more than three decades of service.

The City of Long Beach purchased Queen Mary and permanently moored her in California. Conversion removed boilers, machinery, and many lower-deck spaces to create a hotel, restaurants, museum attractions, and convention facilities. The ship opened to the public in 1971, but changing operators and ambitious commercial schemes complicated stewardship. Ghost stories and entertainment attracted audiences while sometimes eclipsing engineering, labor, migration, and wartime loss. Corrosion, leaking systems, and deferred maintenance eventually generated alarming repair estimates and closures.

Long Beach resumed direct control in 2021 and undertook urgent structural and safety work before reopening the ship. Queen Mary is listed on the National Register of Historic Places, yet preservation of a steel vessel permanently afloat requires continuous inspection, painting, drainage, ventilation, and expensive renewal. Its surviving public rooms, machinery spaces, cabins, and decks document both ocean-liner glamour and the work behind it. The ship's history spans depression-era policy, wartime mobilization, mass travel, technological obsolescence, urban redevelopment, and the difficult economics of conserving an object the size of a city block.