Watson Brake: North America's Oldest Known Mound Complex

Watson Brake is a ring of 11 earthen mounds in Ouachita Parish, northeastern Louisiana, built by hunter-gatherers from around 3500 BC. It is the oldest known large mound complex in North America, about 2,000 years older than nearby Poverty Point and older than the first pyramids of Egypt. Its dating in the 1990s overturned the long-held idea that only farming societies could build monumental earthworks.

Background: the Archaic period

In North American archaeology, the Archaic period covers roughly 8000 to 1000 BC, after the end of the Ice Age and the era of big-game hunters such as the Clovis culture. Archaic peoples lived by hunting, fishing and gathering. Over time they settled more securely in rich environments such as river valleys, where fish, game, nuts and seeds were plentiful.

The Lower Mississippi Valley, with its rivers, swamps and oxbow lakes, was one of these rich environments. During the Middle Archaic, roughly 6000 to 3000 BC, some communities in the region began to heap up earth into mounds. Small Middle Archaic mounds are known at several Louisiana sites, but Watson Brake is by far the largest and best studied of this early group.

The site

Watson Brake lies on an old river terrace on the edge of the Ouachita River floodplain, near the city of Monroe. A “brake” is a local word for a swampy backwater, and the site takes its name from the nearby Watson Brake swamp.

The complex consists of 11 mounds connected by low ridges, forming an irregular oval roughly 280 metres (about 900 feet) across. The mounds range from about 1 metre to 7.5 metres (3 to 25 feet) in height. The largest, usually called Mound A, stands on the northern side of the ring. The enclosed central area was kept largely free of debris, which suggests it was an open plaza.

The amount of earth moved was considerable. Estimates of the total volume run to tens of thousands of cubic metres, all carried in baskets or other containers by people without draught animals or metal tools.

How it was built

Excavations showed that the mounds were not raised in one effort. They grew in stages over several centuries, with layers of earth added on top of earlier surfaces. Some of these surfaces show signs of occupation, such as hearths, burnt material and tools.

Building appears to have begun around 3500 BC and continued until about 2800 BC, after which the site was abandoned. Construction may have been concentrated in particular phases, separated by periods when people lived at the site without adding much to the mounds.

The builders were mobile or semi-mobile hunter-gatherers. Food remains found at the site include freshwater fish such as drum and catfish, freshwater mussels, deer, turkey and other small animals, together with seeds and nuts. The fish species and other evidence suggest that the site was occupied at least during the warmer months, possibly on a seasonal basis.

People also left behind stone tools, fire-cracked rock from cooking, small stone beads and baked-clay objects. These fired-earth cooking objects are early forerunners of the famous clay balls later made in large numbers at Poverty Point.

How it was dated

Watson Brake was known as a group of mounds before archaeologists studied it closely, but its age was unknown. Mounds of this size were normally assumed to belong to later farming societies, such as the Woodland or Mississippian cultures, which built most of the mounds of eastern North America after about 1000 BC.

A team led by archaeologist Joe W. Saunders, then of Northeast Louisiana University (now the University of Louisiana at Monroe), investigated the site in the 1990s. They used several independent lines of evidence:

• Radiocarbon dating of charcoal and other organic material from mound layers and occupation surfaces.
• Luminescence dating, which measures when heated objects such as the baked-clay pieces were last fired.
• Soil development, since the soils that had formed on top of the mounds needed thousands of years to develop.
• Artefact types, especially stone tools typical of the Middle Archaic, and the complete absence of pottery.

All these lines of evidence pointed in the same direction. In 1997 the team published their results in the journal Science, dating the complex to between about 5400 and 5000 radiocarbon years before present. A fuller report followed in American Antiquity in 2005.

The finding was at first met with some scepticism, because it contradicted textbook views. Further work at Watson Brake and other Middle Archaic sites has since confirmed that hunter-gatherers in Louisiana were building mounds well before 3000 BC.

Purpose and meaning

No one knows exactly why Watson Brake was built. The builders left no writing, and there is no surviving oral tradition linked to the site. Archaeologists have suggested several roles, which are not mutually exclusive:

• A gathering place where scattered bands met at certain seasons to feast, trade, arrange marriages and perform ceremonies.
• A territorial marker, showing a group’s claim to a rich stretch of river and swamp.
• A monument whose repeated building strengthened shared identity across generations.

Some researchers have proposed astronomical alignments in the arrangement of the mounds, but these claims are not widely accepted. Unlike many later Native American mounds, Watson Brake is not known as a major burial site.

Legacy and significance

Watson Brake changed ideas about the relationship between farming and monuments. In the Old World, monumental building is usually associated with farming societies, though Göbekli Tepe in Turkey is an important exception. Watson Brake showed that in North America, too, hunter-gatherers with abundant wild resources could organise labour on a large scale.

It also placed northeastern Louisiana at the beginning of a long mound-building tradition. About 2,000 years later, people in the same region built the much larger earthworks of Poverty Point, and later still the Mississippian culture raised great platform mounds at sites such as Cahokia. There is no direct line from Watson Brake to these later sites, since mound building in Louisiana paused for many centuries after about 2800 BC, but the idea of the earthen monument had deep roots.

Watson Brake lies on private land, has no visitor facilities and is not open to the public. Its remoteness and the care of its owners have kept it in good condition.

By the numbers

Timeline

• c. 6000–3000 BC: Middle Archaic period in the Lower Mississippi Valley.
• c. 3500 BC: Mound building begins at Watson Brake.
• c. 2800 BC: Construction ends and the site is abandoned.
• c. 1700–1100 BC: Poverty Point earthworks are built in northeastern Louisiana.
• 1990s: Joe W. Saunders and colleagues investigate and date the site.
• 1997: Results published in Science establish Watson Brake as the oldest known mound complex in North America.
• 2005: A detailed report is published in American Antiquity.

Why it matters

Watson Brake shows that monumental architecture in North America began with hunter-gatherers more than 5,000 years ago. It forced archaeologists to rethink the link between farming and complex society, and it marks the start of the long tradition of earthen mounds in eastern North America.