Incorporated in 1846, the Pennsylvania Railroad opened its first sixty-one mile stretch from Harrisburg to Lewistown in 1849, crossing the Susquehanna River on a twenty-three-span wooden truss bridge at Rockville that would later be replaced by an iron bridge and, eventually, by the landmark 1902 stone-arch Rockville Bridge. By 1850, the PRR line reached Altoona, where it established a repair shop for engines and cars that later made the city the largest railroad shop town in America. - ExplorePAhistory.com