This study addresses the issues of market integration in railroad industry analyzing the export-bound grain transportation. A spatial analysis involving four origin states (Illinois, Iowa, Minnesota and Nebraska) and two destinations (Mexican Gulf and Pacific Northwest) is conducted in order to determine if pricing practices by the same or different railroads in different regions are consistent. A system of structural equations is estimated and dynamic regression tests are conducted because of the dynamic nature of interregional trade and arbitrage activities. The results indicate that grain transportation market by rail is not perfectly integrated. This is primarily due to numerous mergers and combining of railroads that took place during the last twenty years.