Meanwhile, the State of Maryland granted the B&O a charter to build a line from Baltimore to Washington, D.C., in 1831, and the Washington Branch was opened in 1835. This line joined to the original mainline at Relay, Maryland, crossing the Patapsco River on the Thomas Viaduct (which remains one of the B&O's signature structures). This line was partially funded by the state of Maryland, and was operated separately until the 1870s, with Maryland receiving a 25 percent cut of gross passenger receipts. The B&O's charter also forbad further taxation of the railroad, and that no-tax provision was upheld in the 1840s after Baltimore City tried to tax it. This Washington Branch line was built in stone, much like the original mainline. By this time, however, strap rail was no longer used for new construction. Most of the stone bridges on the Old Main Line did not last long, being washed out by the periodic flooding of the Patapsco River and replaced at first by Bollman Truss bridges. The Annapolis and Elk Ridge Railroad to Annapolis connected to this line at Annapolis Junction in 1840. As an unwritten condition for the charter, it was understood that the state of Maryland would not charter any competing line between Baltimore and Washington, and no such charters were approved until well after the American Civil War, when the Pennsylvania Railroad acquired a railroad on the Delmarva Peninsula, which had the power to build short branch lines, so it was able to connect to Washington through Bowie, Maryland.