Ancient Ohio Earthworks timeline

The Geological Formation of the Ohio Valley (2 million to 9000 BC): Enormous glaciers helped reshape the Ohio Valley many thousands of years ago. The edge of the flat, glaciated region is prominent along a line just west of Serpent Mound, Chillicothe, and Newark. After the last glacier retreated northward, the new tributaries of the Ohio River, such as the Scioto or the Great Miami, often followed wide valleys created by the earlier, larger rivers. These valleys have rich soil, laid over the sand and gravel till left behind by the glaciers, and wide terraces at different levels that later became prime locations for earthworks.

Paleoindians in the Great Valley (13000 to 8000 BC): While glaciers still covered much of North America, people first arrived from Asia by the ancient land bridge to Alaska or by boat. Over many generations they spread across the continent. People we call “Paleoindians” were in the Ohio Valley as early as 13,000 years ago, living in wandering bands, gathering plants, and hunting. Their distinctive spear points have been found in the bones of long extinct ice age animals like the wooly mammoth. They were skilled stone workers, and discovered the beautiful rainbow-colored stone from Ohio's Flint Ridge, used by their descendants for centuries and still prized by flintknappers today.

Archaic Indians (8000 to 1500 BC): When the glaciers melted, the tundra and pine forests of eastern North America were replaced by the “eastern woodland” ecology we know today: hardwood forests threaded by many rivers and streams. The large ice age animals became extinct or moved northward, replaced gradually by deer and other woodland animals. This new environment also presented a wealth of nuts, fruits, plants and edible roots. The “Archaic” people began to plant seeds and tend gardens, making eastern North America one of only a handful of places on earth where agriculture began without outside influence.

The Adena Culture (1500 BC to AD 100): The first burial mounds in the Ohio Valley mark new beliefs and customs. People still moved periodically, but they began to make pottery and erect thousands of great earthen burial structures around the Ohio and its tributaries, showing a strong sense of community. Archaeologists named this culture “Adena” after Thomas Worthington’s Chillicothe estate, where a mound excavation in 1906 revealed its typical practices. The Adena produced beautiful artifacts, and developed elaborations on mound architecture, including circular ditches, pavements, and walls. The later Hopewell culture overlaps with the Adena, both in years and in territory. The Hopewell built enclosures near or even around Adena earthworks. The Adena and the Hopewell may have been the same people whose practices changed, or neighbors with different views but mutual respect.

The Hopewell Culture (100 BC to AD 400): Great new inspirations marked the coming of Ancient Ohio’s “Golden Age.” People began to assemble over many generations, creating complex earthworks, enormous in scale, precise in geometry, and often aligned with celestial events. And beneath carefully mounded layers of earth they left elaborate burials and beautifully crafted objects, evidence of their artistic skill and the great reach of their trade networks. This culture is called "Hopewell" because its richest ceremonial site was part of Mordecai Hopewell's farm, just west of Chillicothe, at the end of the 19th century. From its southern Ohio heartland, Hopewell practices and interactions spread across much of North America. By about AD 400, forests were reclaiming the geometric earthworks, and the communities’ focus shifted from these vast ceremonial centers to growing villages, and new ways of life.

The Fort Ancient Culture (1000 to 1650): By the year one thousand, the large-scale cultivation of corn was transforming life in ever-larger villages. These ideas were shared with groups along the Mississippi River (notably at Cahokia and other large cities). These practices in the central Ohio Valley have been named “Fort Ancient Culture” because one of their villages was built near the much older (Hopewell era) walls of Fort Ancient. Unlike some of their contemporaries to the south, the Fort Ancient Indians did not build large pyramid mounds, or live in large cities; but they did create small flat-topped mounds and effigy mounds, including the continent's most famous, the Great Serpent.

The Great Dying (1492 to 1650): The most tragic event in the history of American Indians, and of all North America, is the Great Dying. Probably more than 80% of all native peoples died from European diseases within the span of a few decades. New infectious diseases swept across the continent much faster than the new people did; so when Europeans finally arrived in the Great Valley of the Ohio, the damage had already been done. With the death of elders in particular, memories and knowledge were often lost. These huge plagues also undermined ancient beliefs: people watched desperately as the old cures failed against the new diseases. All this sudden death may help explain why so little is known today of the ways and beliefs of the ancient earthwork builders.

Tribes in the Ohio Valley (1700 to 1843): By 1650, the ancient earth-building traditions had faded. The Iroquois were moving through the Ohio country, scattering other tribes and trying to control the fur trade. Soon afterward, other tribes came in from the north and east. The first French and British traders encountered Miami, Wyandot, Ottawa, Shawnee and Delaware (Lenape) people, among others. None of these groups had proven, direct connections with the earthwork builders. But it is clear that all Eastern Woodland Indians share a common heritage, and that the earlier Adena, Hopewell, and Fort Ancient people are among its ancestral sources.

Europeans Encounter the Earthworks (1750 to 1850): The first Europeans in the Ohio Valley were impressed by the earthworks, but quick to classify them according to their own ideas. Many sites were named “forts” due to a superficial (though later disproven) resemblance. More importantly, most settlers, and even scholars at the time, could not accept the possibility they were built by the ancestors of the Indians they were meeting in the area. Racism and ignorance led many Euro-Americans to concoct bizarre theories that they were built by transplanted Egyptians, or Israelites, or a Welsh tribe, or the Vikings! This confusion persisted until the early twentieth century.

Early Appreciation for the Earthworks (1750 to 1850): The founders of the United States knew and admired the earthworks along the Ohio. George Washington and Thomas Jefferson both argued for their preservation. Jefferson's Secretary of the Treasury Albert Gallatin was another eager scholar of ancient America, and expressed disgust for people who belittled the achievements of the Indians. Public interest in the mounds was at its peak by the mid-1800s, when two citizens of Chillicothe, Ephraim Squier and Doctor Edwin Davis, set out to survey the earthworks of the entire Mississippi and Ohio river system. With support from Gallatin, their work became the first publication of the new Smithsonian Institution.

Destruction and Preservation (1750 to the Present): Ohio Valley tribes did not live on the old earthwork sites, but they sometimes added their own burials. The settlers, though, were quick to build among the earthworks: they were often in ideal spots for water access or for farming. Many were destroyed and many more were cut down by treasure hunters. By the late-1800s, scientific archaeology began to study them. Frederic Ward Putnam, “the father of American archaeology,” traveled from Harvard University to investigate the Great Serpent Mound, and saved it from destruction. Often the processes of archaeology found and saved valuable artifacts, yet destroyed the earthworks. Modern farming, graveling, and urban sprawl are still taking a toll on the ancient sites, despite strong efforts by the Ohio Historical Society, the National Park Service, the Archaeological Conservancy, and others.

Earth, Art, and Culture (Present and Future): The idea that earth shapes space and can be designed to reflect the deep meanings in a culture, is still with us. Consider the great gardens of Europe, or China, or our own massive interstate highway embankments! The ancient earthworks can remind us how the manipulation of the landscape always carries important meanings as well as aesthetic power. Artists and landscape architects understand fully that blending nature and artistry, especially at a vast scale, is always intriguing. On the new University of Cincinnati campus, sinuous earthen embankments (by world-renowned designer George Hargreaves) weave the campus together, enclosing space, directing movement, and marking distant vistas; students walk among a series of winding earthworks and massive mounds (explicitly inspired by Ancient Ohio) as they go from class to class.