On December 7, 1941, the Imperial Japanese Navy launched a surprise attack on the United States Navy's Pacific Fleet at Pearl Harbor. The attack destroyed 13 warships and 188 aircraft, and killed 2,403 US military personnel and 68 civilians. Fearing a possible attack against the American president, Franklin Delano Roosevelt , the secret service decided to reinforce his security… and that of his transport. The next day the president was going to address Congress to request a State of War and they did not have adequate transportation for their transfer. In addition to the limited time available, they encountered a budget problem... a federal law prohibited spending more than $750 for the purchase of the presidential car . A member of the secret service, who years before had intervened in the capture of Al Capone, recalled that he had confiscated an armored car, a 1928 Cadillac Town Sedan 341A .
That Cadillac was equipped with the latest technology of the time:siren, hidden lights, police radio, a shield of almost 3 cm. thick and bulletproof windows. It only required mechanical work and a facelift on a car that had been sitting in Treasury Department storage for several years. The next morning F.D. Roosevelt was traveling to Congress in the mobster's car:
I hope Mr. Capone doesn't mind said Roosevelt
The president continued to use the Cadillac until the Ford Motor Company was able to adapt the Lincoln 1939 V12 . As the cost continued to exceed the $750 limitation, it was settled with a $500 per year lease.
Sources:CNet, The Forgotten History Blog, History