Effective and sufficient support for the transportation of oversized and overweight (OS-OW) loads on the nation's transportation system is important to a vibrant economy. The availability of advanced tools and technologies based on geographic information systems (GIS) has increased considerably the ability of transportation policy makers to analyze vehicle routing data better. The Texas Department of Transportation recently initiated a research effort to analyze the routes of historically permitted OS-OW loads. The primary objectives of this research included the development of criteria for assigning current and projected OS-OW groups to an improved road network, the identification of strategic infrastructure improvements to accommodate such loads, and the development of optimal and alternative routes for priority load groups between the most common origins and destinations. As part of the project, the research team developed a highly efficient GIS-mapping approach and converted a massive data set of OS-OW permit routes into a GIS format. The mapping approach enabled batch processing and directly queried, retrieved, and stored data from and to an Oracle database. This paper presents part of the findings of this research, with a focus on the GIS mapping process of the historical OS-OW permit routes. The GIS approach will be particularly valuable for those states that are, or will be, automating their process for OS-OW permitting through GIS-based tools. In addition, the research provides valuable lessons for other states that are looking for a workable solution to analyze effectively mass historical OS-OW routing data.