Louis Slimmer began the wrestling program at Proviso Township High School in 1936 and retired from coaching in 1954.

He coached his teams to seven Illinois state wrestling championships, including the first ever in 1937. His teams won the first four state titles, six of the first seven and seven of the first nine. Slimmer's teams finished third in 1941, 1946 and 1952.

Slimmer coached 18 individual state champions, 26 runners-up, 16 third-place finishers and five fourth-place finishers.

A number of his wrestlers competed in college, placing in conference and national tournaments, and many of his protégés went on to become coaches.