The document analyzes the pre-settlement drainage network of the Upper Sangamon River Basin in Illinois. The researchers used several methods to estimate the pre-settlement configuration, including analyzing early 1800s survey maps, alluvial soil maps, and topography. They found that the current channel network is 2-3 times more extensive than the pre-settlement estimates. However, over 80% of surveyed 1800s channels were within 50 meters of alluvial soils, suggesting the estimates identified similar channel locations. The expanded modern network results from significant human impacts, making the basin's natural evolution more difficult to study. Understanding pre-settlement configurations helps model drainage formation in low-relief glaciated areas.