The U.S. Geological Survey (USGS) in cooperation with NOAA, developed a regression model for estimating August mean baseflow per square mile of drainage area to help resource managers assess relative amounts of baseflow in streams with Maine Atlantic Salmon habitat. The model was derived from August mean baseflows computed at 31 USGS streamgages in and near the Gulf of Maine Atlantic Salmon Habitat Recovery Units. An ordinary least squares regression model estimates August mean baseflow per unit drainage area using two explanatory variables: percentage of the basin underlain by sand and gravel aquifers, and the basin mean July precipitation. This model provides the means to estimate August mean baseflow in cubic feet per second per square mile of basin area on user-selected ungaged sites throughout Maine south of 46º 21′55″ N latitude. Estimates will support prioritization of habitat conservation and restoration work for those reaches that offer baseflow refugia during summer low-flow periods, and thus have the potential to be high-quality Atlantic Salmon habitat. This data release includes 3 excel tables of data used in these analyses.