Property Record
Pentoga Road (National Forest Road 2446) over Brule River
Architecture and History Inventory
| Historic Name: | Pentoga Road Bridge (P-19-0013) |
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| Other Name: | |
| Contributing: | |
| Reference Number: | 245696 |
| Location (Address): | Pentoga Road (National Forest Road 2446) over Brule River |
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| County: | Florence |
| City: | |
| Township/Village: | Florence |
| Unincorporated Community: | |
| Town: | 41 |
| Range: | 16 |
| Direction: | E |
| Section: | 28 |
| Quarter Section: | |
| Quarter/Quarter Section: |
| Year Built: | 1930 |
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| Additions: | |
| Survey Date: | 20222025 |
| Historic Use: | bridge |
| Architectural Style: | NA (unknown or not a building) |
| Structural System: | Warren Truss |
| Wall Material: | Metal |
| Architect: | Wisconsin State Highway Commission |
| Other Buildings On Site: | N |
| Demolished?: | No |
| Demolished Date: |
| National/State Register Listing Name: | Not listed |
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| National Register Listing Date: | |
| State Register Listing Date: |
| Additional Information: | 2025: The Pentoga Road Bridge is located on Pentoga Road (aka Cherry Avenue) over the Brule River between Florence County, Wisconsin and Iron County, Michigan at the northern border of the Chequamegon-Nicolet National Forest. Pentoga Road is a two-lane dirt and gravel road with dense woodland along both sides of the road west of the Brule River; the woodland east of the river opens to a clearing containing the unincorporated community of Pentoga, Michigan. The Pentoga Road Bridge was constructed in 1930 and is a one-span, riveted steel, Warren pony truss bridge with verticals. It measures 60 feet in length and 16 feet in width and carries a single lane of traffic over the Brule River. Each truss is comprised of four panels with riveted gusset plates at connections between diagonal/vertical members and upper/lower chords. Built-up diagonal and vertical members are comprised of batten-connected angle bars. Built-up upper chords, lower chords, and end posts are comprised of batten-connected channel beams. The foundry mark of the Illinois Steel Company’s South Chicago works (indicated by “Illinois S USA”) is visible on some channel beams. Diagonal steel cables were added in 1988 between floor beams and the upper portions of each end post; these are anchored to the end posts via threaded rod and nut connections. Additional midspan strengthening added at that time consisted of steel beams welded below the outer faces of both lower chords. The bridge deck is comprised of sawn timber planks that rest on steel stringers; stringers are supported by a series of steel floor beams. Two parallel railings (comprised of narrow channel bars) run the length of the bridge along the inside faces of both trusses. Fixed bearings sit atop cast-in-place reinforced concrete abutments with steel sheet piling added in front of each abutment. All steel bridge components are painted, though failing paint has resulted in substantial corrosion at various locations. 2023: According to the Highway Structures Information System, P-19-0013 was originally constructed in 1930. The single lane bridge is located in a rural setting in the Town of Florence, Florence County in the Chequamegon-Nicolet National Forest and trends east-west between the Wisconsin and Michigan state borders. P-19-0013 is a single, simple span Warren pony truss bridge with verticals. The bridge members are steel. Each span consists of four, fifteen-foot panels between end posts and verticals. The end posts and the upper chord are built-up with battens along the underside. The vertical members and diagonal members are comprised of angle flanges built-up with battens. The connections are riveted and at bolted at gusset plates connecting the vertical members and diagonal members. The lower chords consist of steel angles built-up with battens. Two horizontal steel channel guardrails were installed on either span. The decking consists of two timber stringers on top of perpendicular wood planks. The wood planks are supported by additional I-beam stringers on I-beam floor beams. The I-beam floor beams connect to the vertical and diagonal joints. Suspension cable ties reinforce the superstructure by wrapping the underside of the I-beam floor beams bolting through the end posts and upper chords with large eyebolts. According to the construction log for P-19-0013 in the Highway Structures Information System, the superstructure was reinforced in 1988. The bolted connections, such as the cable ties and the I-beam floor beams, may indicate these were later alterations made to reinforce the bridge. Each section of the superstructure underside is reinforced with cross angle rods which are bolted to the I-beam floor beams. The substructure consists of poured concrete abutments that were or have been wrapped in steel sheeting that has then reinforced with an I-beam crib. Heavy, large rock riprap surrounds abutment. pony truss bridge |
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| Bibliographic References: | Files and Construction records, “P-19-0013”, Highway Structures Information System (HSI). |
| Wisconsin Architecture and History Inventory, State Historic Preservation Office, Wisconsin Historical Society, Madison, Wisconsin |