Detroit:

An important civic sculpture in Detroit is "The Spirit of Detroit" by Marshall Fredericks at the Coleman Young Municipal Center. The image is often used as a symbol of Detroit and the statue itself is occasionally dressed in sports jerseys to celebrate when a Detroit team is doing well. A memorial to Joe Louis at the intersection of Jefferson and Woodward Avenues was dedicated on October 16, 1986. The sculpture, commissioned by Sports Illustrated and executed by Robert Graham, is a 24-foot (7.3 m) long arm with a fisted hand suspended by a pyramidal framework.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". Who sculpted the Joe Louis memorial?
Robert Graham