This bridge, one of the longest (in total length) covered bridges left in the country, is a true gem of the covered bridge community. Despite its age, the bridge still manages to retain a good amount of historical integrity (with most of the significant changes that have been done now being old enough to be historical in their own right), this bridge is also notable because of its age, length, unusual truss configuration, as well as its beautiful setting in the downtown of historic Bath, N.H.
The Bath Bridge was first constructed in 1832, although this is some times questioned as there was an earlier structure at this site. An examination of its stone abutments and also the truss configuration indicate that it was originally a 3 span system, with two larger spans and a smaller span sandwiched in the middle.
The truss system employed is very unique, and deserves a good amount of attention. This truss has been sometimes classified as a Burr arch variation, or erroneously identified as either a Paddleford or Haupt truss (both types this bridge predate). In truth its neither, and does not conform to any standard truss type. A arch (similar to a Burr type) runs across the 3 original spans, and the main truss is comprised of diagonal elements sloped towards the center of the span, running across two vertical elements and terminating in the upper chord.
Information such as the bridge wright or any other information about this truss type have been lost to time, so we have no idea who built this or the reasons why such a unusual truss type was devised. The most likely explanation was a creative bridge wright working to avoid patent royalties for the more common truss types. An interesting note is that there is another example of this bridge type existing nearby in Thetford Vermont (see the Sayres Covered Bridge, commonly mis-identified as a Haupt Truss)
In the first few decades of the 20th century, as with most of the covered highway bridges in New Hampshire, this bridge was modified to increase its load capacity with the addition of laminated wooden arches. From east to to west, a arch was added with no modification to the first and second span, which doesn't distract terribly from the original configuration. The third span had some unusual modifications made, due in part to the fact that the Boston & Maine railroad ran under the 3rd span. A pier was made midway through the span, and a third arch connects the 2nd pier to this pier. For the remainder of the bridge there is no added arch, instead 3 wooden piles support the remainder of the truss. Inside the truss this creates an inconsistent look which mildly detracts from the experience.
The bridge is well taken care of, having received rehabilitation's over the years as needed (the most recent being 2013-14). Its important that this bridge continue to receive this level of care, as its quite special due to the aforementioned points. Its also notable as a survivor among covered bridges, as both longer spans and "in-town" bridges were the most susceptible to replacement over the years due to higher traffic/weight needs.