We measured the percent live canopy and height of randomly-selected cottonwood trees at three sites: Deerlodge Park on the Yampa River (DLP), Island Park on the upper Green (ILP), and Canyonlands National Park on the lower Green (CAN). From these same trees we took increment cores to understand differences in tree growth in each forest over time. This dataset includes four tabular digital files. The file "cottonwood_characteristics_dlp_ilp_can.csv" includes data on location, age, height, live canopy cover, and fire history. The files "dlp.txt", "ilp.txt", and "can.txt" contain annual tree ring width for trees at DLP, ILP and CAN.