In 1811, Henry Marie Brackenridge walked up the Cahokia Creek in search of ancient mounds. Brackenridge lived in St. Louis – a town known for years as Mound City – and had been told that the biggest mounds in the area could be found on the grounds of a Trappist monastery on the other side of the Mississippi River. After walking for about four miles into the floodplain, he found himself in front of the largest earthen mound ever constructed north of Mexico (Young and Fowler 2000: 3–5). Two years later, he described this moment in a letter to his good friend, the former president of the United States Thomas Jefferson (1962 [1814]: 187):

Brackenridge spent the remainder of that day exploring the dozens of mounds that made up the site. He found flint, animal bones, and pottery littering the surface and concluded that “if the city of Philadelphia and its environs were deserted there would not be more numerous traces of human existence” (1962 [1814]: 186).

Henry Marie Brackenridge was perhaps the first European American to recognize the significance of Cahokia and its related sites in the St. Louis area.