The Digital Geologic Units of Great Smoky Mountains National Park and Vicinity, Tennessee and North Carolina consists of geologic units mapped as area (polygon) features. The data were completed as a component of the Geologic Resources Evaluation (GRE) program, a National Park Service (NPS) Inventory and Monitoring (I&M) funded program that is administered by the NPS Geologic Resources Division (GRD). The data were captured, grouped and attributed as per the NPS GRE Geology-GIS Geodatabase Data Model v. 1.3.1. (available at: http://science.nature.nps.gov/im/inventory/geology/GeologyGISDataModel.cfm). The data layer is available as a feature class in a 9.1 personal geodatabase (grsm_geology.mdb). Attributed geologic contact lines that define the geologic unit polygons are present within the Geologic Contacts (GRSMGLGA) data layer. The Geologic Units (GRSMGLG) GIS data layer is also available as a coverage export (.E00) file (GRSMGLG.E00), and as a shapefile (.SHP) file (GRSMGLG.SHP). Each GIS data format has an ArcGIS 9.1 layer (.LYR) file (GRSMGLG_GDB.LYR (geodatabase feature class), GRSMGLG_COV.LYR (coverage), GRSMGLG_SHP.LYR (shapefile) with map symbology that is included with the GIS data. See the Distribution Information section for additional information on data acquisition. The GIS data projection is NAD83, UTM Zone 17N. That data is within the area of interest of Great Smoky Mountains National Park.