Judge Fred W. "Duke" Slater, seated, of University of Iowa's undefeated football team of 1921, huddles with former teammates at a luncheon honoring him on Aug, 13, 1958, at the Sherman Hotel in Chicago. Other players are, from left, Aubrey Devine, Les Belding, Bill Kelly and Glen Devine. (Chicago Tribune via AP)

Frederic "Duke" Slater poses for a photo in 1921 when he was a tackle on the University of Iowa football team. Slater was the NFL’s first African-American lineman, and often the only Black player on the field. After retiring, he broke down more racial barriers to become a judge in Chicago. (Chicago Sun-Times via AP)

From left, Rep. William Dawson, Cook County Municipal Court judge candidate Frederick "Duke" Slater and Adlai Stevenson, candidate for governor, are shown in this Oct. 31, 1948, photo. Slater was the NFL’s first African-American lineman, and often the only Black player on the field. After retiring, he broke down more racial barriers to become a judge in Chicago. (Chicago Sun-Times via AP)

Iowa football player Frederick "Duke" Slater poses for a photo in 1921 Slater was the NFL’s first African-American lineman, and often the only Black player on the field. After retiring, he broke down more racial barriers to become a judge in Chicago. (Chicago Sun-Times via AP)