Garrett Island is an island located in Cecil County, Maryland, 1.8 miles (2.9 km) from the mouth of the Susquehanna River, directly west of Perryville and north of Havre de Grace. It is managed by the U.S. Fish and Wildlife Service as part of the Blackwater National Wildlife Refuge. The island is crossed by the CSX Susquehanna River Bridge on the north side and the Thomas J.