Climate
Check the weather forecast for Collinsville from NOAA.
The Mississippi River makes this area humid, though temperatures are generally moderate. Storms can occur at any time of the year. July and August are hottest and most humid, and January and February are cold, with occasional snow. Normal temperatures range from 21°F in the winter to 90°F in the summer -6°C to 32°C, but summer highs of 100°F and winter lows of 0°F are not uncommon 38°C and -18°C.
Flora and fauna
Wildlife at the site are legally protected, and many live in small forested areas. Deer sightings are common while ducks and other birds may be spotted as you roam the well-marked trails.
Free printed guides help you to identify some of the plants and trees at the site, while carefully-maintained garden areas show off the types of plants grown in prehistoric times.
History
Built by Mississippian Indians between 600 and 1300 AD, Cahokia was the largest prehistoric city in all of what became the United States. Then covering six sq mi 16 sq km, Cahokia was a melting pot of Indian groups. The city included large fields of corn, wooden houses for thousands of people, grand open plazas, and about 120 earthen mounds.
Though the city was abandoned in the 1300's, French and later American settlers arrived in the 17th and 18th century and again began growing crops. Even in the early 1800's, archeologists recognized that there was something unique here, but the land continued to be used for farming for the next 125 years. In the 1930's, the United States government considered making the site into a national park, but ultimately decided against the idea. The state of Illinois then purchased an initial plot of land including Monks Mound, and continues to expand and operate the park today through the Illinois Historic Preservation Agency. Cahokia Mounds State Historic Site remains one of the few World Heritage sites in the United States which is not run by the federal government.
Cahokia Mounds was designated a National Historic Landmark in 1964, listed on the National Register of Historic Places in 1966, and named a World Heritage Site by the United Nations in 1982.
Landscape
Cahokia Mounds is in the Mid-Western Plains a few miles from the banks of the Mississippi River in the ridge and swale floodplain known as the "American Bottom." This area included numerous lakes, sloughs, marshes and streams, many of which formed in the old abandoned river channels. Bottomland forests dominated around the water sources. Today, cities have built up throughout the American Bottom, but this 2,200 acre 9 km2 oasis gives an idea of how the lands may have appeared long ago.
Understand
The main features of the site are the 69 remaining man-made mounds, the largest of which is Monks Mound, around 100 ft 30 m tall. The rest of the 2,200 acre 890 hectare site consists of many grass covered mounds that vary in size and shape, several interpretive trails and signage, a reconstruction of the Woodhenge sun calendar, and reconstructions of the palisade/stockade walls.