Sheeted clastic dikes offer geologists a new way to count the Missoula floods. The dikes formed coincident with flooding and grew larger with each flood event. Each flood is preserved as one or more fill bands in dikes. Each subbasin preserves a different flood count. Here we test whether clastic dikes grew larger in basins visited by more floods by documenting the number of fill bands in dikes at 300 sites throughout the Columbia Basin.