1442401 is the ZIP code for Marathon, Florida. It is located in Monroe County and includes portions of the city of Marathon, Key Colony Beach, and Duck Key. Marathon is a city on the Florida Keys, about halfway between Key Largo and Key West. The area is known for its tropical beaches, lively fishing culture, and solitude. It is popular with tourists, especially during the winter months, when it is perfectly situated to take advantage of the warm waters and sunny days of the Gulf of Mexico.