Even American universities took scant notice of Cahokia and other homegrown sites before the second half of the 20th century. They preferred sending their archaeologists to Greece and Mexico and Egypt, where the stories of ancient civilizations were comfortably distant and romantic. The few people who championed Cahokia and its neighboring mound centers at East St. Louis and St. Louis fought a mostly losing battle against development and neglect for the better part of a century. The latter two sites—among the largest Mississippian communities in their own right—were destroyed and paved over. And though Monks Mound, named for French monks who once lived in its shadow, became a tiny state park in 1925, it was used for sledding and Easter egg hunts. The rest of Cahokia was largely ignored—built on and only sporadically studied—until the 1960s.
And that's when history demonstrated its fine sense of irony, because the biggest construction project to tear into Cahokia would also put it on the map. President Dwight Eisenhower's interstate highway program, though a massive undertaking that changed America's landscape as dramatically as the railroads once did, contained provisions for the study of archaeological sites in its path. This meant more money for excavations than had ever been available, as well as a clear agenda for where to dig, when, and how fast. With two highways slated to skewer the ancient city—I-55/70 now bisects Cahokia's north plaza, creating a road sandwich with Collinsville Road, a quarter mile to the south—archaeologists began to systematically study the site. What they found was nothing less than revelatory.
It became apparent that Cahokia was more than just a stupendous pile of earth or a ceremonial site where scattered tribes congregated once in a while. Nearly everywhere they dug, archaeologists found homes—indicating that thousands of people had once lived in the community—and many of these homes had been built within a very brief span of time. In fact, the whole city seemed to spring to life almost overnight around 1050, a phenomenon now referred to as a "big bang." People streamed in from surrounding areas, built houses, and quickly constructed the infrastructure of a new city—including several mounds with buildings on top and a grand plaza the size of 45 football fields, used for everything from sporting events to communal feasts to religious celebrations.