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.

The rocky high ground on the island's west side is the remains of the volcanic core.

[2] In 1622, the island was given to Edward Palmer as part of a land grant by King James I, and the earliest documented European presence dates to 1637 when William Claiborne established a trading post on the island.

[2][5] In the same year, Maryland troops evicted Claiborne's Virginia traders from the Upper Chesapeake region and built Fort Conquest on what was then called "Palmer's Island.

"[5] Watson Island was purchased by the Baltimore and Ohio Railroad (B&O) in the 1880s so a bridge could be built across the Susquehanna River at that point.