Cobban Bridge

Information and Findings From Wisconsin Historic Bridge Inventory

Discussion of Bridge

Significance of the Cobban Bridge By Diane Kromm, Wisconsin Historic Bridges Recording Project, Summmer 1987

The Modern Steel Structures Company of Waukesha constructed the Yellow River Bridge across the Chippewa River in 1908. The firm, incorporated in 1900, developed the most modern and complete steel structural plant in the West. Between 1916 and 1918, the Wisconsin-Minnesota Power & Light Company built a hydroelectric dam four miles downstream from the bridge, putting the site under water. The townships of Eagle Point and Arthur arranged to have the 486-foot span dismantled and re-erected 15 miles upstream near the village of Cobban. The Cast Stone Construction Company, in Eau Claire, installed the new concrete substructure. Crombley and Thailacker, a Milwaukee bridge-building firm, apparently erected the steel work. The Yellow River Bridge is the oldest of four Pennsylvania truss bridges remaining in Wisconsin.

Truss Bridge Intensive Survey Form Bridge: B-09-965

Measuring over 480 feet in length, the Cobban Bridge crosses the Chippewa River in an east-west direction on County TT about 5 miles southwest of the city of Cornell. The structure is a pin-connected overhead truss with two identical Pennsylvania spans bordered by channel and angle-iron railings. It rests on concrete abutments and a single concrete pier. In addition to portal, top-lateral and sway bracing, the bridge's webbing is stiffened with sub-diagonals, extended sub-verticals, and intermediate, horizontal struts. The wood decking is protected by metal runners.

The structure was originally located about 15 miles downstream where it was known as the "Yellow River Bridge," presumably because its site was near the confluence of the Chippewa and Yellow Rivers. It was erected at county expense in 1908, the Modern Steel Structural Steel Company of Waukesha [Wisconsin] apparently served as both fabricator and contractor for the superstructure. In 1915, the Wisoconsin-Minnesota Power and Light Company approached the Chippewa County Borad of Commissioners with a plan to build a hydroelectric dam about 4 miles downstream of the bridge. Since the impounded waters would inundate the river crossing, the company proposed relocating the exiting bridge superstructure. In April, 1916, after extended negotiations, the county finally approved the dam project and the company agreed to build a completely new bridge.(A)

The decision attracted the attention of the small trading village of Cobban located about 15 miles upstream on the west back of the Chippewa. Cobban had no bridge, the nearest crossings being about 5 miles north at Cornell and an equal distance south at Jim Falls. With the strong support of Cobban merchants, local voters in December 1916 agreed to pay the cost of dismantling the abandoned Knife River Bridge, sledding the structural steel to Cobban, and reassembling the bridge at its present location.. The entire project was completed by 1919. L.G. Arnold, a professional contractor from Eau Claire, put in the new concrete substructure, while Cromby and Thailacker, a bridge-building firm from Milwaukee, supervised the steel work.

Published by the Wisconsin DOT in 1998 as part of the Historic Highway Bridges in Wisconsin project.

Statement of Significance (Wisconsin DOT 1998 Intensive Survey):

Fabricated in 1908, the Cobban Bridge was the oldest of four Pennsylvania truss bridges surviving on Wisconsin highways in 1986. It is an excellent early Twentieth Century example of the type, which is basically and overhead, sub-divided Pratt truss with a polygonal upper chord.. Developed specifically for long spans in 1875 by the Pennsylvania Railroad (hence the name) the Pennsylvania truss was modified a decade later by the Chesapeake & Ohio Railway, which introduced intermediate horizontal struts to increase rigidity of the web. Another characteristic feature, also seen on the Cobban Bridge, is the upward extension of sub-verticals for the purpose od stiffening the long upper chord members. As is customary on highway bridges of the 1890s and 1900s, the Cobban Bridge displays built-up sections for its structural members -- a practice that was later replaced by the use of rolled sections, as can be seen on two previously extant Pennsylvania trusses of the 1930s.

In addition to its engineering significance as a highly representative example of its types, the Cobban Bridge is historically significant as one of the most ambitions cases of bridge moving in Wisconsin. Since metal truss bridges were specifically designed to to be easily transported and assembled, it is not surprising that several were moved from one location to another. It is remarkable, however, that a small community should fund and suprvise the relocation a structure the size of the Cobban Bridge, which displays the longest, pre-World War II, highway, truss spans surviving in the state. Although the village of Cobban has long since vanished, the bridge remains as palpable evidence of its easlier, commercial aspirations. The structure is still recognize as a major landmark by local residents, whose campaign to commemorate the bridge resulted in the erection of an historical marker near the crossing in 1986.

Published by the Wisconsin DOT in 1998 as part of the Historic Highway Bridges in Wisconsin project.

Bridge Considered Historic By Survey: Yes