We pulled data from the US Bureau of Transportation Statistics which has compiled a spreadsheet of major dams in the United States that are 50 feet or more in height, or with a normal storage capacity of 5,000 acre-feet or more, or with a maximum storage capacity of 25,000 acre-feet or more.

We then filtered the data by the year the dam was constructed. Using latitude and longitude coordinates provided with the data, we used Factlook‘s geocoding feature to plot the location of each dam on the map. The legend displays the period covered as well as the number of dams built during that time period. Clicking on a marker displays a window with specific to that dam (see image below).