Brad Plumer mentions an underappreciated point:
The War on Drugs, which has contributed more to our mass-incarceration orgy than anything else, strikes me as more than just Jim Crow for the 21st century. After all, as Lazare notes, in 1989 even Jesse Jackson was talking about applying "antiterrorist policies" on drug users and traffickers. Charlie Rangel was attacking Reagan for being soft on the drug menace.
Indeed, when I read Randall Kennedy's Race, Crime, and the Law a few years ago, I was surprised to learn that Rangel was one of the movers behind creating the powder-crack sentencing gap. Not that he specifically wanted to create a gap, as such, but in the 1980s he was head of a Select Committee on narcotics and favored super-harsh sentences for crack as a way to try to protect inner city neighborhoods.