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B & O Railroad Potomac River Crossing
The Baltimore and Ohio Railroad Crossings at the Potomac River are a set of railroad bridges that span the Potomac River between Maryland Heights, Maryland and Harpers Ferry, West Virginia in the United States.
==Description and history==
Two bridges comprise the current crossing. The more recent bridge is a deck plate girder bridge dating to 1930-31 which curves across the river, carrying the Baltimore and Ohio Railroad (B&O) main line to Martinsburg, West Virginia. (This line is now the CSX Cumberland Subdivision.) The older bridge is a steel Pratt truss and plate girder bridge dating to 1894, carrying the B&O Valley line (now the CSX Shenandoah Subdivision) toward Winchester, Virginia along the Shenandoah River. A tunnel was built at the same time as the 1894 bridge to carry the tracks through Maryland Heights and to eliminate a sharp curve. The western end of the tunnel was widened in conjunction with the construction of the second bridge to allow the broadest possible curve across the river.
Just downstream of the 1894 bridge, almost at the confluence of the Potomac and Shenandoah Rivers, are the ruins of two previous bridges on the same alignment. The newer of the bridges was a Bollman truss bridge that carried rail and highway traffic from 1870 until 1936, when it was swept away by a flood. The Valley line section of the "Y"-shaped bridge dated to 1851, and was one of the earliest Bollman trusses in existence. The remainder of the bridge was destroyed in the Civil War, to be replaced by temporary structures.〔
The B&O's first bridge over the Potomac was an covered wood truss, comprising six river spans plus a span over the Chesapeake and Ohio Canal. The single-track bridge was designed by Benjamin Henry Latrobe, II and opened in 1837.〔 Latrobe designed a "Y" span for the route to Winchester, which was added to the bridge in 1839.〔 An earlier road bridge, a timber covered bridge, had been built c. 1824,〔Note: Harwood (p. 44) states an opening date of 1829.〕 replacing Harper's Ferry, which had operated since 1747.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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