The current bridge is the third attempt to span the waterway at this site. The first was a wooden swing bridge, completed in the spring of 1876 after three local men raised $47,000 in stock to build it as a toll crossing. That structure served for nearly two decades before being replaced in 1895 by a steel swing bridge built by the King Bridge Company. The steel swing bridge had its own troubles: in 1905, a ship called the Northern Wave collided with it and damaged the center swinging section. The section was replaced, and in 1920 another ship nearly repeated the disaster, only stopping in time by dropping its anchor, which snagged on the canal bottom. By the 1950s, the 54-year-old swing bridge had been declared a menace to navigation on the busy Keweenaw Waterway, and the decision was made to replace it entirely.

The bridge that replaced it was a feat of mid-century engineering. More than 35,000 tons of concrete and 7,000 tons of steel went into the structure, designed by the Chicago firm Hazelet and Erdal. The American Bridge Company built the superstructure and Bethlehem Steel provided the structural steel, with the Al Johnson Construction Company serving as general contractor. The cost ran between $11 and $13 million, depending on the source. When it opened in 1959, the bridge carried U.S. Highway 41 and M-26 across the waterway on an ingenious double-decked liftspan. The lower deck had rails embedded in the road surface for trains, while the upper deck served vehicles. The span could be partially raised to a middle position, letting small and medium boat traffic pass while cars continued across above. For large ships, the full lift cleared the waterway entirely. For trains, the span dropped to its lowest setting.

Rail service ended in 1982, and with it the need for the lowest bridge position during the boating season. Since then, the bridge stays at its middle or raised position through the summer months, descending to the bottom only for maintenance, repair, or the annual freeze-up that opens the lower deck to snowmobile traffic. The intersection where US 41 and M-26 approach the bridge from the south has earned the nickname the Yooper Loop -- a nod to the colloquial term for residents of Michigan's Upper Peninsula. Hancock and Houghton, the twin cities the bridge connects, hold an annual celebration called Bridgefest to commemorate the opening that united their communities. In June 2022, the bridge received designation as a National Historic Civil Engineering Landmark, placing it among a select group of structures recognized for their contribution to engineering history.

For all its tonnage and engineering distinction, the Portage Lake Lift Bridge matters most for what it makes possible. Without it, the northern half of the Keweenaw Peninsula -- the towns of Calumet, Laurium, Copper Harbor, Eagle Harbor, and dozens of former mining communities -- would be accessible only by water or by a long detour around the waterway's eastern end. The bridge is not just a crossing; it is the lifeline of a region. Michigan Technological University students in Houghton cross it to reach restaurants in Hancock. Miners once crossed earlier versions to reach the shafts on Quincy Hill. Today, tourists cross it on their way to the Keweenaw National Historical Park, and every winter, snowmobilers cross its lower deck in a tradition as practical as it is peculiar. From the air, the bridge is a thin silver bar across the dark water of the waterway, the hinge point of a peninsula that copper built.