Occupied c. 700-1400, Cahokia Mounds in Illinois. are remnants of the largest settlement n. of Mexico eponymously called pre-this.
I suppose this could be a bit confusing. The eponymous here refers to the explorer Columbus, so the response would have been: "What is pre-Columbian?" (in Jeopardy, players have to respond in the form of a question).
Also, with the $800 clue, there was a picture of the building, which would make it more easily identifiable to anyone who has seen it or been there (the first two clues in particular are geared to an American audience familiar with US history).