The National Waterway Network is comprised of a link database and a node database. Links are line strings, which consist of beginning and end points (nodes) with intermediate vertices (shape points). Links represent either actual shipping lanes (i.e., channels, Intracoastal Waterways, sealanes, rivers) or serve as representative paths in open water (where no defined shipping paths exist). Nodes may represent physical entities such as river confluence's, ports/facilities, and intermodal terminals, USACE nodes, or may be inserted for analytical purposes (i.e., to facilitate routing). The NWN databases were developed by Oak Ridge National Laboratory (ORNL) and Vanderbilt University, with input from the National Waterway GIS Design Committee (NWGISDC). The NWGISDC contains members from several agencies, including the U.S. Army Corps of Engineers (USACE), USDOT Bureau of Transportation Statistics (BTS), Volpe National Transportation Systems Center (VNTSC), Maritime Administration (MARAD), Military Traffic Management Command (MTMC), Tennessee Valley Authority (TVA), U.S. Environmental Protection Agency (EPA), U.S. Bureau of Census, U.S. Coast Guard, and the Federal Railroad Administration (FRA). Several data sources were used to create the network. Therefore, network links vary in scale. The majority of the inland links are at 1:100,000 scale(derived from 1:100,000 scale Digital Line Graph files). Off-shore links were derived from variable scale NOAA Navigational Charts. Therefore, the off-shore links vary in scale, with larger scale NOAA charts used in harbor/bay/port areas, and smaller scale NOAA charts used in open waters. All links in the USACE (non geo-coded) Waterway Link Network are represented in the NWN. The USACE network was used as a base for the NWN; 'USACE links' form a contiguous subset within the NWN, and can be extracted through queries on the 'link number' (linknum) field in the link database (where linknum<1000000). Additional (non- USACE) links and nodes were added to the USACE network to more realistically represent shipping patterns. Approximately 200 USACE ports are geo-coded in the node database, including the top 150 ports. ORNL initially developed databases for the inland waterways; Vanderbilt constructed databases for the off-shore waterways. ORNL then merged the inland and off-shore databases to form a continuous national network. Vanderbilt revised the inland waterway network through use of USGS Digital Line Graph (DLG) files. Vanderbilt, ORNL, and the U.S. Army Corps of Engineers Waterborne Commerce Statistics Center (WCSC) are continuously enhancing and performing validation tasks to improve the accuracy of the NWN.