This excerpt taken from the UNP 10-K filed Feb 5, 2010.
1. Nature of Operations
Operations and Segmentation We are a Class I railroad that operates in the United States. We have 32,094 route miles, linking Pacific Coast and Gulf Coast ports with the Midwest and eastern United States gateways and providing several corridors to key Mexican gateways. We serve the western two-thirds of the country and maintain coordinated schedules with other rail carriers for the handling of freight to and from the Atlantic Coast, the Pacific Coast, the Southeast, the Southwest, Canada, and Mexico. Export and import traffic is moved through Gulf Coast and Pacific Coast ports and across the Mexican and Canadian borders.
The Railroad, along with its subsidiaries and rail affiliates, is our one reportable operating segment. Although revenues are analyzed by commodity group, we analyze the net financial results of the Railroad as one segment due to the integrated nature of our rail network. The following table provides revenue by commodity group:
Although our revenues are principally derived from customers domiciled in the United States, the ultimate points of origination or destination for some products transported are outside the United States.