National Monte Cristo Day is observed every year on September 17, primarily in the United States. This day celebrates the Monte Cristo sandwich, a fried ham and cheese sandwich that evolved from the French croque monsieur. The croque monsieur, which originated in the late 19th century, features ham and cheese between slices of bread, topped with melted cheese. The Monte Cristo, believed to have developed in the U.S., is typically egg-dipped and pan-fried, with variations that may include turkey and can be served with powdered sugar and preserves. The holiday was established in 2015 by Bennigan's, a casual dining restaurant chain known for its Monte Cristo sandwich. People celebrate by enjoying Monte Cristo sandwiches at restaurants or making them at home, often sharing pictures on social media with specific hashtags.