The St. Louis Mercantile Library, founded in 1846 in downtown St. Louis, Missouri, was originally established as a membership library, and is the oldest extant library west of the Mississippi River. Since 1998 the library has been housed at the University of Missouri-St. Louis as a Special Collections library within the Thomas Jefferson Library. The majority of library materials can be assigned to one of four categories: the General (Core) Collection, the John W. Barriger Railroad Library, the Herman T. Pott National Inland Waterways Library, or the Art Museum. The collections of the St. Louis Mercantile Library have been named a City Landmark by the city of St. Louis, Mo., due to the cultural significance of the library.