Out of the ashes of the Great War came the freewheeling cultural renaissance that was the Jazz Age, but the decade-long party of flapper dresses and bootlegging came to a crashing halt with the Crash of '29 - triggering the Great Depression and the New Deal that would help America get back on its feet, just in time for another, greater war.
During the Great Depression, levels of crime actually dropped. During the 1920s, when life was free and easy, so was crime. During the 1930s, when the entire American economy fell into a government-owned alligator moat, crime was nearly non-existent. During the 1950s and 1960s, when the economy was excellent, crime rose again.