Between 2,200 and 1,500 years ago, the Hopewell Culture flourished across the eastern half of North America, centered in what is now southern Ohio, and became one of the continent’s most influential cultures. The Hopewell peoples traveled great distances to gather materials for ceremonial crafts, obtaining copper from the Great Lakes, shells from Florida, mica from the Carolinas, and obsidian from Yellowstone. They built walled ridge-top enclosures such as Fort Hill and Spruce Hill and major floodplain earthwork complexes such as Junction and nearby Hopeton and Seip Earthworks. These low-elevation monuments were typically enclosed by earthen walls up to 12 feet high, laid out in large and often remarkably precise circles and squares, surrounding from a few to several dozen acres and often associated with mounds and walled promenades leading to nearby rivers. Some architectural features were aligned to major astronomical events, and mounds could contain human burials, sacred art pieces, or apparently nothing, suggesting ceremonial purposes that remain uncertain. Constructing these immense complexes required a substantial and well-organized workforce, despite Hopewell society being primarily based on hunting and gathering with only limited reliance on crops such as squash, sunflower, and small-seeded annuals, while maize was not yet a mainstay and people tended to live in small households. At the Hopewell Mound Group, a dirt mold of a carrying basket found in Mound 25 showed a soil capacity of 27 pounds, indicating that creating Mound 25 alone would have required roughly 1.5 million baskets of earth, apart from the site’s three miles of walls and its other 40 mounds. This scale of labor has led to speculation that Hopewell ceremonial centers drew large gatherings from great distances. In the Ohio heartland, dozens of landscape-scale earthen constructions were created without dense population centers or overlords, at the same time that monumental public works were rising among the Mayans, Romans, and Chinese dynasties, leaving enduring monuments of earth and art of stone as evidence of an extraordinarily artistic, sophisticated, and complex culture.