The Summer Island site, designated 20DE4, is an archaeological site located on the northwest side of Summer Island, in Delta County, Michigan. It is classified as a stratified, multi-component site with Middle Woodland (c. 100 B.C–500 A.D.), Upper Mississippian (c. 1000–1500 A. D.) and Early Historic/Protohistoric occupations (c. 1500–1700). It was listed on the National Register of Historic Places in 1971.