Croghan Island Mill is a historic saw mill complex and concrete dam located near Croghan in Lewis County, New York. The mill complex consists of three blocks; the mill building main block, cold storage block, and office block. The main block is a five-by-three-bay, 2 1/2-story gable-roofed structure sheathed in clapboard, approximately 30 by in size. The cold storage block is a 1-story, gable-roofed addition to the north side of the main block. The office block is a 1 1/2-story, shed-roofed addition projecting south of the main block. The complex also includes the wheel house and flume box in a 1 1/2-story ell projecting off the main block. The concrete dam was built in 1906 and has an approximately 2-story drop. The mill was listed on the National Register of Historic Places in 2010.