Hart-Miller Island State Park is an island state park in Maryland. It is located in the Chesapeake Bay near the mouth of Middle River. The park is accessible only by boat and features a 3,000-foot (910 m) sandy beach. The area—at the time comprising three islands—Hart, Miller, and Pleasure—with a total land surface of 250 acres (100 ha)—was acquired by the state in the late 1970s. A dike was built joining Hart and Miller islands into Hart Miller Island in 1983, and the subsequent containment area was filled with Baltimore harbor approach dredge material from the Patapsco River over the next 20 years.