The U.S. Geological Survey (USGS) has a long history of working cooperatively with the South Carolina Department of Transportation to develop methods for estimating the magnitude and frequency of floods for rural and urban basins that have minimal to no regulation or tidal influence. As part of those previous investigations, flood-frequency estimates have been generated at selected regulated streamgages. This is the data release for the report which assesses the effects of impoundments on flood-frequency characteristics by comparing annual exceedance probability (AEP) streamflows from pre- and post-regulated (before and after impoundment) periods at 18 USGS long-term streamgages, which is defined as a streamgage with 30 or more years of record, in Georgia, South Carolina, and North Carolina. For an assessment of how differences in such statistics can be influenced by period of record and hydrologic conditions captured in those records, which could be considered as natural variability, AEP streamflows at an additional 18 long-term USGS streamgages that represent unregulated conditions in those three states were computed and compared for the first and last half of those records. This data release contains the tables and software input and output files from the report Effects of impoundments on selected flood-frequency and daily mean streamflow characteristics in Georgia, South Carolina, and North Carolina (Feaster and Musser, 2023). These tables contain information about the streamgages used in the analysis. The tables are contained in the zip file Impoundments_tables.zip, which includes 8 tab-delimited txt files, and a formatted Excel file of all the tables used in the publication. Two additional files, PeakFQ_files.zip and WREG-Archive.zip include input and output files from the analysis.