Lower Grand River Bridge, Carries Louisiana Highway 997 (LA 997) over Bayou PigeonLower Grand River, Plaquemine, Iberville Parish, LA

Significance: This pontoon swing bridge has significance as a distinctive example of a movable bridge. Its significance is demonstrated by the presence of distinctive engineering and design features of the pontoon swing bridge type, which is characterized by a floating pontoon span, pivot arm, and mechanical systems to operate the movement of the pontoon and approach aprons. The bridge exhibits alterations to the pivot pile, pivot arm, and the control house that result in a minor loss of integrity, but continues to clearly convey the significant features of the pontoon swing bridge type. This bridge was determined eligible for listing in the National Register of Historic Places in 2013 under Criterion C: Design/Engineering at the state level of significance.
Survey number: HAER LA-33
Building/structure dates: 1957-1958 Initial Construction
Building/structure dates: 1998-1999 Subsequent Work
Building/structure dates: 2003 Subsequent Work
Building/structure dates: 2009 Subsequent Work