Zion is a city in Lake County, Illinois, United States. The population was 22,866 at the 2000 census, and estimated at 24,303 as of 2005. The city was founded in July 1901 by John Alexander Dowie. He also started the Zion Tabernacle of the Christian Catholic Apostolic Church, which was the only church in town. It was built in the early 1900s and burned down in 1937.