Transportation planning models and network simulation software are currently utilized by many rail companies to accurately predict the impact on service quality and net revenue due to changes in traffic level or mix, train schedules or blocking plans, yard performance, fluctuations in the level of dynamic resources (e.g., number of locomotives, crews, or rail cars), and changes to the physical network. However, geographic information systems have not been fully integrated into rail network simulation and planning models or technology. This paper focuses on the potential benefits, applications, and uses of GIS for the planning and modeling of railroad networks. A case study of how Esri technology (MapObjects) is currently being used by a major U.S. railroad corporation to integrate GIS into their network planning and modeling software is presented.