Mount Orne Covered Bridge, Lancaster New Hampshire
The Mount Orne Covered Bridge was built across the Connecticut River between Lancaster, New Hampshire, and Lunenburg, Vermont to replace an earlier bridge on the site which was destroyed by the flood of 1905. The Berlin Iron Bridges Company of Berlin, Connecticut completed the Mount Orne Bridge in 1911. The towns of Lancaster and Lunenburg shared the construction costs of the interstate bridge, and continue to contribute equally to its maintenance. The Mount Orne Bridge is the only crossing of the Connecticut River directly between those towns.
The Mount Orne Bridge and another covered bridge across the Connecticut River about 37 miles to the north at Columbia, New Hampshire are the only highway bridges remaining in the state of New Hampshire which are supported by Howe trusses. (One other highway bridge of the same type remains in Vermont at Stowe.) The Mount Orne and Columbia bridges, which were completed in successive years (1911-12), are also the last covered bridges built on public highways during the period of covered bridge construction in New Hampshire and Vermont, which began about 1820.
The Howe truss, which was introduced about 1840 with its combination of wood and iron structural members, represents the transition from wood to iron bridges. The lower initial cost of the Howe structure compared with that of wholly iron or steel construction undoubtedly accounts for its extraordinarily late use at the two lightly traveled crossings served by the Mount Orne and Columbia bridges. The Mount Orne Bridge is reported to have cost only $6,678 despite damage caused by flooding during its construction.
Bridge Description
The Mount Orne Covered Bridge crosses the Connecticut River between Lancaster, New Hampshire, and Lunenburg, Vermont. The low water line on the west (Vermont) side of the river marks the boundary between the states. Most of the bridge, therefore, stands in New Hampshire; the state boundary sign is mounted 32 feet inside the west (Vermont) portal.
The Mount Orne Bridge consists of two spans, each of which is supported by two flanking wood-iron Howe trusses. The principal iron components of the trusses are the paired tension rods which connect the top and bottom chords between adjoining panels of criss-crossed wood compression members. The trusses lack the Howe patent iron angle blocks to accept the ends of the compression members; wood angle blocks serve in their place. Iron tension rods also connect horizontally the top chords and the bottom chords to increase the lateral rigidity of the structure.
The structure rests on abutments and central pier which are constructed of stone. The upper half of the east abutment has been faced with concrete; the rest of the abutment consists of irregular stone blocks mortared together. The pier is built of stone slabs which have also been faced with concrete. On its upstream (north) side, the pier flares outward toward the river bed to deflect floating debris and ice. The west abutment consists of stone slabs mortared together; the upper third of it has also been faced with concrete.
The Mount Orne Bridge has an overall length of 267 feet, divided into two nearly equal spans of 133 feet (east) and 134 feet (west). The bridge has an overall width of 20.5 feet, with a 15.5-foot roadway. The floor (and road surface) consists of planks laid on edge and parallel to the trusses. The current legal load limit posted on the bridge is six tons.
On the exterior, the trusses (and side walls) of the bridge are sheathed with unpainted flush boards hung vertically. Similar siding protects the ends of the trusses immediately inside the portals. The siding stops short of the eaves to leave strip openings along the tops of the walls. The gable ends are also sheathed with unpainted flush boards hung vertically. The portal openings are rectangular.
A medium-pitch gable roof covers the entire bridge, with overhangs both at the eaves and the gables. The roof is sheathed with corrugated metal sheeting.
The Mount Orne Bridge has the numbers (New Hampshire) 29-04-08 and (Vermont) 45-05-03 in the World Guide to Covered Bridges published by the National Society for the Preservation of Covered Bridges. The New Hampshire Department of Public Works and Highways has assigned the number 039/105 to the bridge.
Interior showing south truss (1974)
East portal (1974)
