In 1887, Michigan began building a railway bridge that could open in different ways for passing ships; three bridge designs worked together in one crossing

The rail workers who constructed this bridge in the most remote part of the Upper Peninsula of Michigan back in 1887 have created something that no other bridge in the country has managed to do. Built for function rather than flair, the Sault Ste. Marie International Railroad Bridge, which carries freight trains across the St. Marys River between Michigan and Ontario to this day, combines several different moving bridge styles into one. Its spans today include fixed truss sections alongside a bascule span and a vertical lift span, two genuinely moving mechanisms built to solve two different engineering problems. According to the Library of Congress’ Historic American Engineering Record, it is extremely rare to see this combination of structures used together. This is a fine example of not building things in America as one big statement.

A bridge that kept changing to accommodate larger ships

While the bridge was originally completed in 1887 as a 9-span, camelback, through truss bridge to allow trains to cross the river and the new Soo Locks canal system, they had initially not included any opening sections. However, as the locks got deeper and wider to allow larger freighters to carry iron ore from Minnesota to the steel mills downstate, the fixed spans caused issues.

Therefore, engineers simply extended the bridge with a swing section around 1895 to allow a new Canadian canal to be built. In the 1910s, another section was added by the Strauss Bascule Bridge Company (the same company that later designed the Golden Gate Bridge in San Francisco) to allow for a bascule section. Finally, in 1959, a vertical lift section was added in place of the original swing span, which was removed entirely as part of the project.

Three bridges, one crossing, and a title nobody competes for

Because that 1959 project removed the swing span for good, the bridge today is built from three span types rather than four. As stated by the cultural resource and preservation firm Gray & Pape, who surveyed the bridge, this makes it the only known bridge in the United States to contain fixed truss, bascule, and vertical lift spans together in a single structure. It is also recognised as the first bridge in the country to use an interlocking mechanism to connect the two leaves of the double-leaf bascule section. The bridge did not become famous, unlike the Mackinac Bridge nearby. However, it does do its job and sits in an area of the country that most Americans would struggle to locate.

Why a 19th-century patch job still matters

This low profile belies the bridge’s importance: the Soo Locks that it crosses are still one of the busiest in the world. Nearly 90% of the United States’ iron ore is transported through them. A 2021 WSLS article on the Soo Locks’ economic impact reported that if the locks were closed for six months, it would cause problems throughout the entire manufacturing supply chain in America. The 1887 bridge, which has been continually fixed over the decades, is the bridge that is stopping this.

It can seem strange that these 19th-century improvised designs get so little credit compared to today’s infrastructure, which is announced with huge press conferences and drawings, yet the Sault Ste. Marie Bridge has never received any recognition yet has continued to be upgraded every decade regardless. Perhaps the message we should take away from this 139-year-old railway bridge, which most people will never see, is that sometimes the best way to make things last is to be willing to continually fix them.