Mound City Group National Historic Landmark is located in Ohio and preserves a significant collection of ancient earthworks built by the Hopewell culture. These mounds, constructed between 100 B.C. and 500 A.D., served various ceremonial and burial purposes, showcasing the advanced engineering and social organization of the people who created them. The site features several large mounds arranged in geometric patterns, reflecting the cultural and spiritual beliefs of the Hopewell. Designated as a national historic landmark in 1964, it offers visitors insight into the rich history of Native American societies in the region and their connection to the land.