Year constructed: c1890
Bridge type: Pin-Connected Pratt Through Truss
National Register of Historic Places status: Listed
Length: 235 feet
Width: 13 feet
Spans: 2
FHWA: 137270
Jurisdiction: Decatur County
Location: River Road over Thompson River, 5.7 miles west of Leon, Section 5, T68N-R26W (Burrell Township)
Details
This medium-scale bridge carries a gravel-surfaced road across the Grand River west of Leon in central Decatur County. The structure consists of a pinned Pratt through truss over the main channel of the river, approaced on the east by a peculiarly configured pony truss/bedstead hybrid span. A combination of stone masonry, timber pile bents and steel cylinder piers forms the substructure. County records are vague about the origins of the Grand River Bridge. It appears that the structure was fabricated and erected at this location circa 1890 by bridge contractors Daniel and Webster. Total cost: $2980.00 for a 128-foot iron span with 100-foot approach. Located near the farm of David Springer, the bridge was carried vehicular traffic at this regionally important crossing for about 100 years, with only maintenance-related repairs to its deck, substructure and approaches.
Pin-connected Pratt configurations were used for virtually all of Iowa's wagon trusses in the late 19th century, executed first in wrought or cast iron and - after the early 1890s - in steel. Thousands of such pinned Pratts were erected throughout the state for crossings both large and small, and numberous examples remain in place today. The Grand River Bridge is distinguished among the surviving Pratts for its early erection date and its well-preserved condition. The bridge is further distinguished by its oddly configured approach span. With an inclined end post on one end and an upright end post on the other, this unique span is a pony truss/bedstead hybrid - the only one of its kind in Iowa and exceedingly rare elsewhere. The Grand River Bridge is thus technologically significant both for its representation of prevailing bridge construction trends in the late 19th century and for its unusual structural configuration [Fraser 1992].