Source: Wikipedia.com- Blenheim Covered Bridge
The longest single span wooden bridge in the world. The bridge was built in 1855 by Nichols Powers of Pittsford Vermont. He devised a bridge of three trusses on a modified panel plan, with huge pine timber posts, braces and counterbraces bolted together. The trusses are of long truss design. The center truss is higher than the two outside ones, and in this center truss he enclosed a single arch of oak which reaches from below the lower chord on up to the ridgepole at the peak of the roof . It is really three concentric arches, one on top of another, and carefully blocked together to allow air to circulate among them. The covered portion of the bridge is 232 feet long, the trusses 228 feet and the clear span of 210 feet between abutments. This is one of only six covered bridges with two lanes. The bridge width is 26 feet.