Many high-latitude fluvial systems are adjusting to base-level changes since the last glaciation. Channels that experienced base-level fall may still be incising, often through glacial diamictons (tills). These tills can be quite competent, behaving more like weak bedrock than unconsolidated sediment, and erode at a fast pace, thus providing a unique opportunity to test models of channel incision and knickpoint migration in transient systems. Here, we integrate light detection and ranging (LiDAR) topography, strath terrace chronology, and numerical modeling to determine knickpoint migration and incision history of the Le Sueur River in central Minnesota, USA...