A handful of floating bridges have been constructed in Vermont, the most notable of which spans a small pond in Brookfield. The bridge was originally constructed of floating logs in 1820. The logs were replaced several times over the years until 1884, at which time empty barrels were used. State engineers rebuilt the bridge in 1938. At this time, the oak barrels were soaked in hot tar and chained to the wooden frame. Plank sidewalks were also added on either side of the bridge. This sixth bridge, spanning 320 feet, lasted almost 50 years. The current bridge, number seven, was rebuilt with plastic floats filled with synthetic foam. Another noteworthy floating bridge was constructed in Castleton around 1861. The bridge was significantly altered in 1921, due to its rapid deterioration, and completely replaced in 1961.