Broomes Island is a small waterfront community and census-designated place located at the southern terminus of MD 264 in Calvert County, Maryland, United States, on the Patuxent River. It is located approximately 10 miles south of Prince Frederick, the county seat. As of the 2010 census, the CDP had a population of 405.Although Broomes Island is a rather small community, it does have its own post office and zip code, 20615. In November 2007, the United States Postal Service considered closing the small post office and re-routing all mail delivery through the larger St. Leonard post office branch. After residents contacted US Senator Barbara Mikulski about the proposed closure, the postal service decided against closing the post office.Broomes Island is located near the mouth of St. Leonard Creek, the largest tributary of the Patuxent River entirely inside Calvert County. It is in the vicinity of Broomes Island that several key naval battles were fought during the War of 1812.