The Ponakin Bridge is a historic and now abandoned Post truss bridge that spans the Nashua River in northern Lancaster, Massachusetts. This remarkable bridge holds a special place in history due to its unique design and structural significance. Built in 1871 by the Watson Manufacturing Company of Paterson, New Jersey, the bridge served as a crucial transportation link in the area, spanning the Nashua River in an east-west orientation between Massachusetts Route 70 and Ponakin Road, a residential street paralleling the river's west bank.

The construction of the Ponakin Bridge was not only a testament to engineering craftsmanship but also a nod to the history of transportation in the region. The location where the bridge was built had been home to wooden bridges since the 17th century, serving as a vital connection on the major road leading north from Lancaster. However, with the advent of modern highways, the bridge was bypassed by the present alignment of Route 70 in 1965.

What makes the Ponakin Bridge particularly significant is its use of the Post truss design, which was patented by Simon S. Post around 1866. This truss design played a pivotal role in the development of the national railroad network and was utilized in major crossings, including the Union Pacific Railroad over the Missouri River. While the Post truss design itself was never patented, the Ponakin Bridge is unique in that it also incorporates the patented connection and structural details that Simeon Post filed a patent for and received in 1863. This makes the Ponakin Bridge one of the most important and distinctive truss bridges in the country.

Notably, the Ponakin Bridge is also significant as a bridge with cast iron members, placing it in an elite group of historic truss bridges with this feature. The bridge's trusses consist of eight paneled sections with a total span of 100 feet and a width of 20 feet. It rests on sturdy granite stone abutments constructed from rough-cut stone measuring 20 feet in length.

On September 10, 1979, the Ponakin Bridge was rightfully added to the National Register of Historic Places, a well-deserved honor that recognizes its architectural and historical importance. This listing is significant because it acknowledges the bridge's role in shaping the nation's transportation infrastructure and its unique structural qualities. The reference number for the bridge on the National Register of Historic Places is 79000378.

Despite its historical significance, the Ponakin Bridge faced a sad fate. It was closed to traffic in the 1970s and subsequently abandoned, falling into disrepair. The bridge deck, along with other structural elements, deteriorated over time. However, the bridge's rich history and unique design merit preservation and restoration. Instead of waiting for natural disasters or further decay to take their toll, there is a strong case for relocating and restoring the Ponakin Bridge for pedestrian use. Any restoration efforts should be carried out meticulously, with great care taken to retain and replicate all original materials, including the rivets.

For visitors interested in exploring the bridge, there is a dirt parking lot located a short distance from the bridge, known as the Pellecchia Conservation Land & Canoe Launch parking area. Parking at this lot is free, and from here, you can catch a glimpse of the bridge. However, for the best views, a short walk down to the banks of the Nashua River will provide a closer and more intimate look at this historic engineering marvel.

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