Erosion can remain active and changing in landscapes long after tectonic drivers have ceased, potentially due to local-geologic controls, climate changes, or mantle dynamics. We present new fluvial incision histories and terrain analyses of the Colorado River system through the central Colorado Plateau to test ideas about what has caused the highly variable erosion across this post-orogenic landscape. Results clarify that a mysterious Middle Pleistocene (~1.5 to 0.3 Ma) erosional hiatus (baselevel high) occurred in parts of the region, followed by ~250 m of rapid river incision in the central Colorado Plateau over the last ~350 kyr. Our results potentially support the hypothesis that the lengthy hiatus records a planated landscape graded to the Colorado River before it propagated a signal of baselevel fall from integration through western Grand Canyon in the Pliocene. The subsequent, upstream-migrating incision has been partitioned into multiple waves across the landscape due to the local geologic controls of lava damming in western Grand Canyon, salt tectonics in Cataract Canyon, and heterogenous and layered bedrock throughout. A response-time model indicates that this transient baselevel signal has taken 2-4 Myr to reach the central Colorado Plateau and that it can only account for a small portion of total denudation in the middle-late Cenozoic. This seminal landscape’s highly variable and transient erosion highlights the complexity of landscape evolution even in the absence of orogenic-scale tectonics and regardless of climatic controls.