Plum Island is an island in the town of Southold in Suffolk County, New York. The island is situated in Gardiners Bay, east of Orient Point, off the eastern end of the North Fork coast of Long Island. It is about 3 miles long and 1 mile wide at its widest point. Plum Island is the site of the Plum Island Animal Disease Center, which was established by the United States Department of Agriculture in 1954.