What happened to Cahokia Mounds, the largest ancient city in North America?

This extract from an article at Historic Mysteries looks at the demise of the city, linked to major climatic changes that happened centuries before the arrival of the modern industrial world. Cahokia Mounds is a UNESCO World Heritage site.
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In Southern Illinois, situated along the Mississippi River in Collinsville, an ancient settlement that we call Cahokia rose to great power between 800-1200 CE.

Nicknamed America’s Forgotten City or The City of the Sun, the massive complex once contained as many as 40,000 people and spread across nearly 4,000 acres.

The most notable features of the site are hand-made earthen mounds which held temples, political buildings, and burial pits.

Cahokia Mounds are a testament to the highly organized culture of the early Mississippian people who built the largest city in pre-Columbian North America.

The Rise of the Mound Culture

Small villages first emerged along Cahokia Creek beginning around 600 CE. Subsequently, the climate warmed and more rain found its way to Southern Illinois. Thus, villagers could easily grow an abundance of food. As a result, thousands of people migrated to the area around the Mississippi River.

Then as time went on, the Mississippians created a unified culture all their own and began building mounds across their land in the ninth century.

By about 1000 CE, the Mississippians had built the largest civilization in North America. In fact, some people have referred to it as a kingdom, because the Mississippian culture reached up to the Great Lakes and down to the entire southeastern region of North America.

The city became the pre-eminent center of religious and political power and may have even controlled a vast trade network from the Rocky Mountains to the Gulf of Mexico.

Although today we call the site Cahokia Mounds, no one knows the original name of the city. French explorers in the 1600s named Cahokia after the Cahokia tribe, which lived in the area around that time. However, they may not have had any relation to the original mound builders.
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What happened to Cahokia Mounds?

Cahokia was not destined to last. Its collapse is somewhat of a mystery, however, based on research, the following three events may have had something to do with it.

1). Broxton Bird, a climatologist from Indiana University-Purdue University Indianapolis headed a study that he published in 2017. By taking ancient calcite samples in Martin Lake, Indiana, he and his team determined the precipitation levels throughout the years. Their results indicated that beginning around 1250 CE, climate change occurred. Consequently, this was the start of the Little Ice Age, which lasted 500 years. At that time, a dry period resulted. By 1350 CE, there was a serious drought brought on by dry arctic air.

2). Floods often go hand-in-hand with dry spells when large rainfall occurs during droughts. In another study, Samuel Munoz and Jack Williams took core samples up to 2,000 years old from two lakes in the Mississippi floodplain. They saw that prior to 600 CE there were many floods. Then there was a period of no floods until 1200 CE. During the floodless period, Cahokia flourished. After the flood of 1200, the population declined until complete abandonment.

3). The changes in the climate and the flood event may have severely affected corn production. Thus, famine and hunger would have inevitably led to major upheavals in the large population. As a result, Mississippian societies in the region began to collapse. The destruction of the palisades, an increase in sacrifices, and intensified warfare occurred after 1250 CE. By the end of the 14th century, residents had migrated south and east to areas with more stable climates.

Full article here.

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