The U.S. Geological Survey (USGS) developed a regression model for estimating mean August baseflow per square mile of drainage area in cooperation with National Oceanic and Atmospheric Administration (NOAA) to help resource managers assess relative amounts of baseflow in streams with Maine Atlantic Salmon habitat (Lombard and others, 2021). The model was applied to each reach of a stream network derived from select National Hydrography Dataset Plus High-Resolution (NHDPlusHR) data in the State of Maine south of 46º 21′55″ N latitude. The spatial coverage developed from the stream network contains model-estimated mean August baseflow per square mile of drainage area as an attribute of each NHDPlusHR reach. It is provided here as a shapefile (“Maine_Mean_August_Baseflow_Map.zip”) and published as a Web Map Service (WMS) layer that is hosted as a state map layer on the StreamStats web application for Maine (https://streamstats.usgs.gov/ss/). Please note that the regression equation from Lombard and others (2021) used to calculate model-estimated mean August baseflow values was adapted for English units for this application. The adapted equation is as follows: BFaug = -0.623 + 0.00988AQ + 0.241JULYAVEPRE Where BFaug is the mean August baseflow in cubic feet per second per square miles of drainage area; AQ is the fraction of the basin underlain by sand and gravel aquifers; and JULYAVEPRE is the basin-wide average of the mean July precipitation in inches. The model has an adjusted coefficient of determination (R²) of 0.78 and a mean 95% prediction interval of plus or minus 0.183 cubic feet per second per square mile.