Chris Roach of Man-Sized Target finds a "Window To The Past" in the archives of Time Magazine. Specifically, in a story called Attack on Negro Crime, [February 11, 1957 ] which includes this 1957 statistical footnote:

In 1,477 U.S. cities, Negroes, making up an average 11% of the population, accounted in 1955 for an average 35% of the arrests for what the FBI calls "major crimes" (homicide, rape, aggravated assault, robbery, burglary, theft), and 57% of the arrests for crimes involving violence or threat of bodily harm.

A contemporary liberal, such as Eleanor Roosevelt, would have said that this all stemmed from lack of economic opportunity and discrimination, which was a real problem for blacks at the time. They would have said that if opportunities were available, and discrimination against blacks wasn't a factor, then crime would go down. This turns out not to have been the case.