Trunk Line Bridge No. 1

This multiple-span concrete bridge is located in the Champion Beach County Park, about five miles east of the village of Michigamme. The structure carries an abandoned segment of US-41 over the Peshekee River. It is situated between the current highway bridge (to the north) and the steel plate girder bridge of the Soo Line Railroad (to the south). Built in 1914 by the Michigan State Highway Department, the bridge is comprised of a six 40-foot concrete through girders, carried by full-height concrete abutments and solid concrete piers with bullnosed cutwaters. The bridge illustrates prototypical MSHD design and detailing, with two straight girders that carry the concrete slab deck. The modest architectural expression is provided by recessed rectangular panels in the girder walls, which are capped with heavy concrete copings. Cast into the guardrails on both sides is "State Trunk Line Bridge 1914."

In 1913 the Michigan State Legislature passed the State Trunk Line Act, which authorized the designation of a trunk-line network totaling nearly 3000 miles. The act stipulated that the state highway department would design, build and maintain trunk line bridges spanning 30 feet of more, if the county or local government improved three miles of adjacent road. Soon after its passage, a mainline route across Marquette County was designated. The route extended from Marquette, the county seat, westward through Negaunee and Ishpeming to Michigamme on the Baraga County line. Near Michigamme it crossed the Peshekee River. To entice the state highway department to build a bridge here, the Marquette County Road Commission built a three-mile stretch of the road in 1913. The department approved the bridge, turning its design over to MSHD Bridge Engineer C.V. Dewart.

For the crossing, Dewart delineated this large-scale concrete bridge, designating it as Trunk Line Bridge No. 1. The structure would be massive, extending 240 feet and consuming some 600 cubic yards of concrete. It featured, according to MSHD, "reinforced concrete construction throughout, in which all steel is bedded in concrete, which makes an absolutely permanent structure." The department hired contractors Powell and Mitchell of Marquette to build the structure. They completed it in 1914 for a total cost of $11,129.70. The trunk line was later incorporated into US-41, and this bridge carried increasingly heavy traffic until its subsequent abandonment in a highway re-alignment. Today it stands deteriorating and overgrown in a county park.

The concrete through girder that MSHD built here in 1914 used a design that the agency had just developed as a medium-span standard. During the 1910s and 1920s, the highway department delineated straight girders in five-foot increments between 30 and 50 feet for use in a wide variety of application.

"The reinforced concrete through girder is the design generally employed for spans from thirty to fifty feet in both the eighteen and twenty-foot clear roadway from curb to curb," MSHD stated in its Seventh Biennial Report. "This design lends itself in the majority of cases on account of its very shallow floor system, thereby giving the waterway a maximum clearance under elevation of roadway crossing the bridge."

By 1930 the through girder had largely fallen out of favor with the state and county highway departments, but before it was discontinued, perhaps hundreds of thes utilitarian structures were built throughout Michigan. The Trunk Line Bridge No. 1 in Marquette county is technologically significant as the prototype for this important design. It is also historically significant as the first trunk line bridge designed by the state highway department and as a pivotal crossing on one of the Upper Peninsula's most important routes. Although deteriorated, the Trunk Line Bridge No. 1 is today distinguished as on of Michigan's most important vehicular bridges.