The U.S. Geological Survey (USGS), in cooperation with Miami-Dade County, mapped the approximate inland extent of saltwater intrusion in eastern Miami-Dade County in 2018. This approximation required acquisition and compilation of relevant data collected by the organizations: Florida Department of Environmental Protection (FDEP), Florida Keys Aqueduct Authority (FKAA), Florida Power & Light Company (FPL), MacVicar Consulting Inc., Miami-Dade County Regulatory and Economic Resources (MD-RER), the South Florida Water Management District (SFWMD), and the USGS. Data from the selected monitoring wells were entered into a geographic information system (GIS) for analysis and mapping. The approximate saltwater interface is represented by the 1,000-mg/L isochlor at the base of the Biscayne aquifer. The word “approximate” is used because the spatial distribution of monitoring wells is generally insufficient to create a precise representation.