B.B. King performs on stage during the 2013 Crossroads Guitar Festival at Madison Square Garden on April 12, 2013 in New York City.National Journal

As blues fans and music-lovers around the world remember B.B. King, who passed away Thursday, one lesser-highlighted part of his legacy will be his work in prisons.

In 1971, with former attorney F. Lee Bailey, King co-founded the Foundation for the Advancement of Inmate Rehabilitation and Recreation, which pushed for improved conditions in prisons and put on shows for inmates across the country. For his work, King was honored with the Humanitarian Award by the director of the Federal Bureau of Prisons in 1972.

In 1981, King performed for 3,000 inmates in the world's largest walled state prison in Michigan, where Rep. John Conyers was in attendance.

The tales of blues musicians in prison is the stuff of legend, with Huddie "Leadbelly" Ledbetter literally singing his way out of prison. But as someone born in Mississippi as a black male during the Jim Crow era, like many of his fellow bluesmen, King was aware of the likelihood of someone like him winding up in prison.

"People quite often tease me about going to prisons to play my kind of music," King said in an interview in 1990. "I've never been in trouble myself but I think about, it could have just as easily been a B.B. King instead of B.B. King going out there to play," saying he could have easily wound up in prison.

Some of King's most monumental live recordings featured him playing in prison venues, including Live in Cook County Jail. King called his concert with Joan Baez at Sing Sing Prison in New York one of his greatest live performances. He also recorded an album at California's San Quentin, where Johnny Cash recorded his seminal prison recording.

Criminal justice reform is now a major talking point in campaigns, on the Hill, and elsewhere. For King, the advocacy was part of his decades-long life work.

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