Little Rock, the major port on the Arkansas River, lies among the easternmost foothills of the Ouachita Mountains. A marketing centre and the site of assorted manufacturing facilities, the city also is home to various corporate headquarters and convention centres, as well as an array of renovated historic buildings. At the western boundary of the state lies Fort Smith. It is one of the most industrialized cities in the state and serves as a regional business and service centre. The economy of Pine Bluff, some 50 miles (80 km) downriver from Little Rock, continues to depend largely on the surrounding agricultural area, but since the late 20th century it also has become more industrialized and business-oriented. Texarkana, contiguous with the Texas city with the same name, is an important regional rail centre. An urban concentration in northwest Arkansas has emerged in the wake of the rapid growth of retailing in Bentonville, of trucking in Lowell, and of poultry interests in Springdale and other cities of the region.