Along with being a successful entrepreneur and brewer, George Sleeman (Sr.) was also actively involved in local politics. His entrance into local politics was inspired by the prohibition movement and his interest in protecting his brewing business. His political career began when he was elected councillor of the South Ward in 1876. He served as Guelph's first mayor after its incorporation in 1880 and would serve two terms, once in 1892 and again from 1905-1906. George (Sr.) used his position as mayor to contribute to the city's growth as an industrial centre and played a significant role in bringing Ontario Hydro to Guelph. He also used his position to oppose those who sought to ban alcohol locally on three separate occasions in the 1870s.