The Pennsylvania Railroad was one of the five main trunk lines to connect Chicago and St. Louis with the eastern seaboard. Originally a local project designed to safeguard Philadelphia's trade against competition from two sides: the Erie Canal on the north and the Baltimore and Ohio Railroad on the south. Pennsylvania Governor Shunk signed the company's charter on April 13, 1846. It provided for the extension of lines between Philadelphia and Harrisburg to connect with Pittsburgh in the western part of the state. Work began in 1847 and a continuous single-track connection between Philadelphia and Pittsburgh was completed on December 10, 1852. Although originally constructed create competition with out-of-state transportation, the company charter placed a burdensome tonnage rate of five mills per ton-mile in order to reduce competition with the state-owned transportation. This was later reduced to three mills. In 1857, the Pennsylvania Railroad purchased the main line of public works from the state and, as part of the deal, the state agreed to forgo tonnage fees forever. The "forever" part created a legal question, which was resolved when the state supreme court ruled in Mott v. Pennsylvania Railroad Company that it was unconstitutional for the legislature to give away a revenue source in perpetuity. Electrification of the system was initiated in the spring of 1929 and completed in 1938. In 1968, the railroad was merged with the New York Central to form the Penn Central Railroad.