The Basilica of the National Shrine of the Immaculate Conception is a prominent Roman Rite Catholic basilica located in Washington, D.C., United States of America, honoring the Blessed Virgin Mary as the Immaculate Conception, the principal Patroness of the USA. The shrine is the largest Catholic church in the United States and North America, one of the ten largest churches in the world, and the tallest habitable building in Washington, D.C. Construction of this church, notable for its Neo-Byzantine architecture, began in 1920 under Philadelphia contractor John McShain.