This feature class represents known electric power substations within the continental US and Puerto Rico that are located within 20 miles of the coastline. Substations are facilities and equipment that switch, transform, or regulate electric voltage. This data set includes taps, a location where power on a transmission line is tapped by another transmission line. Many large rivers and bays hydrologically related to coastal waters were considered part of the coastline to make this data set as detailed and complete as possible. Therefore, applicable substations as far inland as Washington D.C., for example, are included. This data set is currently incomplete; data for Alaska, Hawaii and all of the US sovereign territories (except Puerto Rico) was not available at the time of creation. Although data for Puerto Rico is present, it dates from before the 2017 hurricane season, so the current validity is questionable. This product will be updated as new data becomes available.