American Bottom
This plain with its rich alluvial soil, served as the center for the pre-Columbian Cahokia Mounds civilization, and later the French settlement of Illinois Country.
The southern portion of the American Bottoms is primarily agricultural, planted chiefly in corn, wheat, and soybean.
The flood plain is bounded on the east by a nearly continuous, 200- to 300-foot high, 80-mile (130 km) long bluff of limestone and dolomite, above which begins the great prairie that covers most of the state.
The most prominent structure is Monks Mound, rising ten stories high at the center of the complex and fronting on a 40-acre (160,000 m2) Grand Plaza.
Cahokia was a complex, planned, and designed urban center with a residential population, farming, and artisan production of refined crafts and goods.
With its location at the confluence of three major rivers, it was the center of a regional trading network reaching to the Great Lakes and the Gulf Coast.
Archaeologists have found remains of a 2-mile (3.2 km) long, defensive wooden stockade that enclosed the central precinct and was rebuilt several times.
Examples of 18th-century French Colonial architecture survive here, including the old Cahokia courthouse and Holy Family Catholic Church, both made with the distinctive vertical-log construction known as poteaux-sur-solle.
As Americans arrived, many residents of French descent moved west of the Mississippi River to St. Louis and Ste.
Brooklyn, Illinois was founded by 1839 as a freedom village by free people of color and fugitive slaves, led by "Mother" Priscilla Baltimore.
Industrialists located many "smokestack" industries here, such as steel mills, chemical plants, and oil refineries, because they ran on Illinois coal.
In addition, the people who built the first bridge from St. Louis across the Mississippi River to Illinois imposed a tax on heavy traffic.
In the early 20th century, dramatic growth in industrial jobs in the American Bottom attracted many European immigrants and African-American migrants.
More than nine feet of floodwater covered the town of Kaskaskia in 1993 after it overtopped the levee; only the spire of the Catholic church and roof of a nearby shrine rose far above the waters.
