Construction of the Detroit Arsenal Tank Plant began in 1940, before the U.S. became directly involved in the war in Europe. The U.S. Army and the Chrysler Corporation hired Detroit architect Albert Kahn, a factory specialist who in 1941 designed 20 million square feet of defense plants, to create a self-contained tank plant. The first tank rolled off the assembly line there on April 24th, 1941, amid cheering spectators. The December 7, 1941, attack on Pearl Harbor thrust the U.S. into the Second World War and tank plant workers into round-the-clock production. The 1941 Lend-Lease Act committed the U.S. to supplying arms to its allies, and during World War II the government contracted with automakers to make tanks, trucks, and planes. William Knudson, president of the General Motors Corporation, led the government's defense production effort and called on Chrysler Corporation president K. T. Keller to build tanks, drawing on the auto industry's mass production capabilities. President Franklin Roosevelt and Eleanor Roosevelt inspected the plant in September 1942, and two months later workers set the monthly record for all U.S. plants by producing 896 tanks. By the war's end the arsenal had built 22,234 tanks, more than one quarter of the tanks produced in the U.S. Tank manufacturing ceased there in 1997.