The Long Island Railroad, the largest commuter railroad in the United States, developed an enterprisewide spatial data warehouse to provide accurate and detailed information on the infrastructure in every department of the railroad. The enterprisewide spatial data warehouse utilizes SDE as the central warehouse; the LIRR uses ArcView GIS with multiple extensions, MapObjects Internet Map Server technology, and MapObjects. The GIS applications support Intranet-based geoprocessing, dynamic segmentation, and work order planning. This presentation describes the LIRR's process used to build the spatial data warehouse, and describes many of the applications used to improve service planning throughout the organization.