When President Franklin D. Roosevelt took office in 1933, one in four Americans was out of work nationally, but in some cities and some industries unemployment was well over 50 percent. Equally troubling were the bank panics. Between 1929 and 1931, 4,000 banks closed for good; by 1933 the number rose to more than 9,000, with $2.5 billion in lost deposits. Banks never have as much in their vaults as people have deposited, and if all depositors claim their money at once, the bank is ruined. Millions of Americans lost their money because they arrived at the bank too late to withdraw their savings. The panics raised troubling...