The Sinnissippi Mounds are a Havana Hopewell culture burial mound grouping located in the City of Sterling. The mounds are a product of the Hopewell Indian tradition which flourished in the Sterling area around 2,000 years ago. At that time, the area was at the center of a vast trade network which stretched up and down the Mississippi River. Mounds such as the Sinnissippi are common throughout the Mississippi and Ohio River Valleys.
The Sinnissippi Mounds are part of the Sterling Park District's largest park, Sinnissippi Park. The area of the park where the mounds are found, on a bluff overlooking the Rock River, was added to the U.S. National Register of Historic Places on May 14, 1979 as the Sinnissippi Site.