High Quality Content by WIKIPEDIA articles! Zion Nuclear Power Station was the third dual-reactor nuclear power plant in the Commonwealth Edison (ComEd) network and served Chicago and the northern quarter of Illinois. The plant was built in 1973, and the first unit started producing power in December, 1973. The second unit came online in September 1974. This power generating station is located on 257 acres (1.04 km2) of Lake Michigan shoreline, in the city of Zion, Lake County, Illinois. It is approximately 40 direct-line miles north of Chicago, Illinois and 42 miles (68 km) south of Milwaukee, Wisconsin.