The U.S. Geological Survey (USGS) has operated streamflow-gaging stations in 1,053 watersheds in the Upper Colorado River Basin (UCRB) since 1894. Currently, 223 of these streamgages are active. This report presents selected watershed characteristics for 10,338 watersheds in the UCRB. These watersheds are compared to the watersheds upstream of USGS streamgages to assess how well the USGS streamgage network represents the physical characteristics of the watersheds in the entire basin. To conduct this assessment, 17 watershed characteristics, including physiographic parameters, land cover types, lithology, and parameters that describe anthropogenic influence, were computed for each of the gaging station drainage basins. The set of 10,338 watersheds in the UCRB was constructed from a previously developed stream-reach network, and the same 17 basin characteristics were computed for each watershed to facilitate comparisons.