Mosque Maryam, or Nation of Islam Temple No. 2, is located in the the former Sts. Constantine & Helen Greek Orthodox Church, constructed between 1948-1952 by the architect Christopher Chamales. The Nation of Islam purchased the church building in 1972, converting it into a mosque and their national headquarters.
At the time it was completed, the building was the largest Greek Orthodox church in the Americas and was said to be seventh-largest church structure in the United States. It was built in a traditional Byzantine style, modeled after Hagia Sophia
in Istanbul, and is constructed of Indiana limestone. The building is topped with a large dome, 70 feet high and 60 feet in diameter, pierced with 24 windows, each 12 feet high. A star and crescent finial was added to the top after conversion to a mosque. The interior was decorated in Cararra marble with traditional Byzantine iconopgrahy and mosaics, most of which was removed when the church was sold to the Nation of Islam. As a church, the seating capacity of the building was 2,300.
Lane, George, and Algimantas Kezys. Chicago churches and synagogues: an architectural pilgrimage, 196. Chicago: Loyola University Press, 1981.