The Union Park Congregational Church first gathered in 1860 as a mission of the First Congregational Church of Chicago. In 1869, construction began on a new gothic revival church building, designed by Gurdon P. Randall. Construction of the building was completed in 1871 and was large enough to hold all of its 1300 members. The building is now listed on the National Register of Historic Places. Following the Great Chicago Fire of 1871, the Mayor's Office, City Council, and General Relief Committee of Chicago were temporarily headquartered in the church building. Another fire in 1911 destroyed the First Congregational Church building and its members decided to merge with the Union Park Congregational Church. Following the merger, the church was renamed the New First Congregational Church. The First Congregational Church moved out of the building in 1976 to Humboldt Park to better serve its primarily Hispanic congregants. The primarily African American congregants who remained renamed the building the First Baptist Congregational Church of Chicago. Both parishes continue to operate today. The Union Park church register contains membership records including baptismal records, marriage records, membership transfers, and lists of deacons and other officers.