Cram was named an assistant professor at the University of California, Los Angeles in 1947, and a professor in 1955. He served there until his retirement in 1987. He was a popular teacher, having instructed some 8,000 undergraduates in his career and guided the academic output of 200 graduate students. He entertained his classes by strumming his guitar and singing folk songs. He showed a self-deprecating style, saying at one time: