Cahokia was the apogee, and perhaps the origin, of what anthropologists call Mississippian culture—a collection of agricultural communities that reached across the American Midwest and Southeast starting before A.D. 1000 and peaking around the 13th century. The idea that American Indians could have built something resembling a city was so foreign to European settlers, that when they encountered the mounds of Cahokia—the largest of which is a ten-story earthen colossus composed of more than 22 million cubic feet of soil—they commonly thought they must have been the work of a foreign civilization: Phoenicians or Vikings or perhaps a lost tribe of Israel. Even now, the idea of an Indian city runs so contrary to American notions of Indian life that we can't seem to absorb it, and perhaps it's this cognitive dissonance that has led us to collectively ignore Cahokia's very existence. Have you ever heard of Cahokia? In casual conversation, I've found almost no one outside the St. Louis area who has.
Our ignorance has deep roots. The first person to write a detailed account of Cahokia's mounds was Henry Brackenridge, a lawyer and amateur historian who came upon the site and its massive central mound while exploring the surrounding prairie in 1811. "I was struck with a degree of astonishment, not unlike that which is experienced in contemplating the Egyptian pyramids," he wrote. "What a stupendous pile of earth! To heap up such a mass must have required years, and the labors of thousands." But newspaper accounts of his discovery were widely ignored. He complained of this in a letter to his friend former President Thomas Jefferson, and with friends in such high places, word of Cahokia did eventually get around. Unfortunately it was not word most Americans, including subsequent Presidents, were very interested in hearing. The United States was trying to get Indians out of the way, not appreciate their history. Andrew Jackson's Indian Removal Act of 1830, which ordered the relocation of eastern Indians to land west of the Mississippi, was premised on the idea that Indians were nomadic savages who couldn't make good use of land anyway. Evidence of an ancient Indian city—one that rivaled the size of Washington, D.C., at the time—would have mucked up the story line.