 His most important project was the Chateauesque design for the 1890 St. Louis City Hall competition, which won the first prize and the job for the firm.In early 1891 George Mann moved to St. Louis to oversee construction of the city hall, and he also established a solo practice there.Later that year, after a brief time back in Minneapolis, where he produced a Beaux-Arts library design for Buffington, Ellis joined Mann in St. Louis.