Ancient America Is Still Here: Earthworks & Mounds You Can Visit

An enormous earthen serpent uncoils along a ridge in southern Ohio, its body curving for more than a quarter mile toward an oval at its head.

Who built it

Serpent Mound is about 1,348 feet long and roughly three feet high — the largest serpent effigy known in the world.

Who built it is genuinely debated. Radiocarbon studies have pointed both to the Adena culture (around 300 BCE) and to the much later Fort Ancient culture (around 1070 CE). Ohio History Connection presents both possibilities.

In northeast Louisiana lies a landscape of six concentric earthen ridges and huge mounds — built more than 3,000 years ago by people who lived by hunting, fishing and gathering.

Who built it

Poverty Point was built and used roughly 1700–1100 BCE. Its builders weren't farmers, which upended older assumptions about who could build monuments this large.

Stone and minerals found here came from as far away as the Great Lakes and the Appalachians, showing exchange networks spanning hundreds of miles.

Around Chillicothe, a cluster of earthworks built roughly 2,000 years ago forms the heart of Ohio's World Heritage listing.

Who built it

People of the Hopewell culture built these geometric enclosures and mounds about 1–400 CE. They were ceremonial gathering places, not towns.

Excavations uncovered objects made from materials carried across the continent — copper from the Great Lakes, mica from the Appalachians, obsidian from the Rocky Mountains and shells from the Gulf Coast.

The largest set of geometric earthworks in the world once covered about four square miles of Newark. Two giant pieces survive: a vast circle and a perfect octagon.

Who built it

The Hopewell culture built these enclosures about 2,000 years ago. The Great Circle is about 1,200 feet across, with walls up to about 14 feet high and an inner ditch.

The Octagon connects to a circle and covers about 50 acres. Researchers have shown its walls line up with the moonrise and moonset points of the moon's 18.6-year cycle.

Above the Little Miami River, earthen walls snake for about three and a half miles along a wooded hilltop.

Who built it

Despite its name, Fort Ancient wasn't a fort. The Hopewell culture built its walls about 2,000 years ago, most likely as a ceremonial enclosure.

The name also causes confusion: the later 'Fort Ancient culture' is a different people, named after this site because they lived nearby centuries afterward.

On the banks of the Etowah River, a 63-foot earthen platform rises over a former Mississippian town.

Who built it

Etowah was occupied roughly 1000–1550 CE by Mississippian people, ancestors of the Muscogee (Creek). Leaders lived and held ceremonies atop the mounds.

Excavations here uncovered carved marble statues and copper plates — some of the most famous Mississippian artworks known.

Twenty-nine mounds ring a grand plaza above the Black Warrior River — the remains of one of the largest Mississippian centers in North America.

Who built it

Moundville flourished roughly 1120–1450 CE. Around 1,000 people are thought to have lived inside its palisade at its peak, with many more in the surrounding countryside.

Over time it became a political and religious center where elites were buried, before the population moved out and the site was used mostly for burial.

On bluffs above the Mississippi, low earthen bears and birds march through the forest — more than 200 mounds, about 31 of them shaped like animals.

Who built it

Most effigy mounds here were built during the Late Woodland period, roughly 700–1100 CE. Older conical and linear mounds at the park date back much further.

The National Park Service works with 20 culturally associated tribes, for whom these remain sacred places.

Across the river from St. Louis sits the largest prehistoric earthen construction in the Americas — and around it, the remains of the biggest city north of Mexico before Columbus.

Who built it

Cahokia was built by Mississippian people and reached its height roughly 1050–1350 CE. Archaeologists estimate its peak population in the range of 10,000 to 20,000 people, though the exact figure is still debated.

The city had a central plaza, a wooden palisade and around 120 mounds, about 70 of which are protected at the state historic site today.