There is no database containing information on all the dams in the United States. The single largest source is the National Inventory of Dams (NID) from the US Army Corps of Engineers which claims to have more than 80,000 dams. I downloaded the entire data from NID and also cleaned it up. This GitHub site provides both the raw data I obtained from NID and also the cleaned data. Also on this site is R code to visualize the data.
I wanted to bundle this data into an R package, but the data is too large and clunky and exceeds CRAN’s data limits (~ 5 MB).