Starting in the 1970s, America's incarcerated population began to rise rapidly. In response to a tide of higher crime over the preceding decade, state and federal lawmakers passed measures that increased the length of prison sentences for all sorts of crimes, from drugs to murder.

But around the mid-1990s, the crime rate began to drop as the number of incarcerated Americans continued to climb. After two decades of the crime decline, local, state, and federal lawmakers have begun to reconsider previous "tough on crime" policies — leading the prison population to drop for the first time in decades in 2010.

Chart credit: The Sentencing Project