The National Hydrography Dataset (NHD) High Resolution flowlines were used as a base to provide additional information on the connectivity of the stream network for the hydrographic basins in and around Montana. In addition to the attributes that are published as part of the NHD data, two fields were added to the attribute table to associate streams that do not have a Geographic Names Information System (GNIS) name with the GNIS name and NHD reachcode of the nearest downstream named flowline. The National Hydrography Dataset (NHD) is a feature-based database that interconnects and uniquely identifies the stream segments or reaches that make up the nation's surface water drainage system. NHD data were originally developed at 1:100,000-scale and exists at that scale for the whole country. This high-resolution NHD, generally developed at 1:24,000/1:12,000 scale, adds detail to the original 1:100,000-scale NHD. Local resolution NHD is being developed where partners and data exist. The NHD contains reach codes for networked features, flow direction, names, and centerline representations for areal water bodies. The NHD also incorporates the National Spatial Data Infrastructure framework criteria established by the Federal Geographic Data Committee. This dataset is NHD Model version 2.2.1. For more information on the NHD High Resolution dataset, see Model Diagram at: http://ftp.geoinfo.msl.mt.gov/Data/Spatial/MSDI/Hydrography.