The Paul Butterfield Blues Band was formed by Paul Butterfield. He brought in keyboardist Mark Naftalin and guitarist Elvin Bishop, both of whom he met as students at the University of Chicago. Guitarist Mike Bloomfield, who he met at the clubs on the South Side of Chicago was the next to join the band. By the first album, the group's line-up was completed with the addition of bassist Jerome Arnold and drummer Sam Lay.