He returned to New Orleans and became a manufacturer and dealer of farm equipment, and an organizer of New Orleans's first electric lighting company. He was elected as a Republican to Congress in 1888, but lost his bid for reelection in 1890 to Matthew D. Lagan, the previous holder of the seat. Coleman was the last Republican to represent Louisiana in Congress until David C. Treen in 1973. Coleman was the last Republican to represent New Orleans in the House until Joseph Cao was elected in 2008.