This pump, designed by Edwin Reynolds (1831-1909) and built by the Edward P. Allis company, is the major component of one of the earliest water-pollution control systems. It was capable of pumping more than a half billion gallons of water a day, the highest-capacity pump in the world when installed. It still is used during the summer to pump water from Lake Michigan into the Milwaukee River upstream of the downtown area. This maintains a current in the lower portion of the river and greatly reduces the concentration of pollutants.

The pump continues in service to this day, 104 years following its initial operation. The original steam engine and boiler plant were removed in 1908, at which time the pump was repowered by an electric motor. The pump house is located on the lake front.