Cahokia Mounds, Illinois
Cahokia Mounds State Historic site is the location of the largest Native American (pre-Columbian) city built within the current territory of the United states. No one knows exactly how large the city was at it's peak. Estimates range from a population of 10,000 to 40,000 in the late 1100s. The city was the center of Mississippian culture which flourished throughout the center of the United States from the 800s AD to the 1500s. The site is the largest and most complex Native American archeological site in the US. It is one of only 21 UNESCO World Heritage Sites in the US and the only one in the Midwest. No one knows what the inhabitants of Cahokia called their city. Cahokia was named after a group of Illiniwek natives living in the area when the French arrived in the 1600s. At that time the city had already been abandoned. Signs of city building at the site date to 600AD. The main period of habitation was from 800-1350AD. During it's height the city sprawled over several square miles and included 120 mound structures as well as countless wooden structures that have not survived.
Today the site is preserved as the Cahokia Mounds State Historic Site. It is managed by the State of Illinois and a non-profit preservation society. The preserved area encompasses 3.5 square miles. There is unfortunately, a two lane highway routed through the middle of the mound complex as well as above ground telephone/power lines. This seems inappropriate given that it's one of the most important historic sites in the US. The park has a large and modern visitor/interpretive center and there are walking paths through out the site. There is a small admission fee for the visitor center but no charge for the paths and parking. The park usually has a dozen or so visitors at any given time but is large enough that it's never crowded. The mounds site is in a rural pocket surrounded by the bleak industrial eastern Saint Louis suburbs. It's a few miles Northeast of East Saint Louis and a few miles Southeast of Granite City. You can see the Granite City steel mills from the top of Monks Mound (the largest mound in the complex) as well as a massive trash pile/landfill and also downtown Saint Louis in the distance. Depending on which way you go, the drive into the park is either depressing, boring or spectacularly grim. As far as scale and historic importance, the only site equal to Cahokia that I've been to in the United States is Chaco Canyon. Cahokia is unfortunately not nearly as photogenic but well worth visiting.