Wiktionary
n. An open-faced sandwich with meat topped with french fries and smothered with cheese sauce.
Wikipedia
The horseshoe is an open-faced sandwich originating from Springfield, Illinois, United States. It consists of thick-sliced toasted bread, often Texas toast, a hamburger patty, French fries, and a "secret" cheese sauce. Common replacements for the hamburger patty include ham, deep fried pork tenderloin, grilled or fried chicken breast and fried fish fillets.
Though cheese sauces vary by chef, it is generally derived from Welsh rarebit. Common ingredients include eggs, beer, butter, cheese, Worcestershire sauce, mustard, salt and pepper.
A "breakfast" horseshoe is also commonly available, replacing the meat and French fries with eggs and hash browns.
A smaller portion, with one slice of bread and one serving of meat, is called a "pony shoe".
Ross' Restaurant in Bettendorf, Iowa, is known for a similar dish called the "Magic Mountain". Instead of a hamburger patty, they top it with steamed loose-meat. It's been enjoyed by politicians and celebrities including President Barack Obama and Bette Midler.