City planner and planning consultant.
In the 1940s, Oppermann advised on federal housing legislation as a planner for the Federal Housing Administration. He was planning director of San Francisco city and county from 1949-58, and was the first director of the Illinois planning agency, predecessor to the Northeastern Illinois Planning Commission. He served as president of the American Institute of Planners and as assistant director of the American Society of Planning Officials. Oppermann lectured in metropolitan planning at Massachusetts Institute of Technology. He was a member of the International Fraternity of Lambda Alpha, Ely Chapter.