Antique Real Photo Postcard. Identified as the Madonna Chapel, the smallest church in the United States, located on Levee Road between Plaque Mine and White Castle, Louisiana. Published by. Divided back, unused. Condition: This is an original photo postcard, not a copy or reproduction. It is in excellent condition. Comments: The Chapel of the Madonna outside White Castle, Louisiana, measures 9 feet by 9 feet, thus nabbing it the title the Smallest Church in the World by Ripleys Believe It or Not. Italian farmer and Louisiana resident Anthony Gullo built this chapel along the Mississippi River near Baton Rouge in 1902 after he prayed to the Virgin Mary for healing.