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The Stillwater Bridge (alternatively known as the Stillwater Lift Bridge, St. Croix River Bridge at Stillwater, is a vertical lift bridge crossing the St. Croix River between Stillwater, Minnesota, and Houlton, Wisconsin. It connects Minnesota State Highway 36 and WIS 64, and is one of two bridges on the river between the Interstate 94 bridge in Hudson, Wisconsin and the U.S. Highway 8 bridge in Taylors Falls, Minnesota, providing a popular and useful alternative to those crossings. (The other bridge is the Minnesota State Highway 243 bridge, in Osceola, Wisconsin)

The bridge consists of ten fixed steel truss spans 1,050 feet (320 m) long in total, including a vertically lifting span 140 feet (43 m) long. It is 23 feet (7.0 m) wide, allowing one lane of traffic in each direction. The lifting span is a Waddell and Harrington type, one of six built in Minnesota and Wisconsin and one of three still remaining today. Built in 1931 to replace a swing bridge from 1910, it was the last bridge of this design to be built in the area. Minnesota and Wisconsin evenly split the $460,174 cost of the bridge.

Because the bridge feeds directly into downtown Stillwater on the Minnesota side, gridlock often occurs and traffic can back up on Minnesota State Highway 36 for many miles, especially on weekends and during the summer. The effect is made worse whenever the bridge is raised. The bridge's mechanisms have remained essentially unaltered since its opening in 1931 and have on occasion become stuck.

In addition, the bridge has been deemed "structurally deficient" by inspectors, receiving a sufficiency rating of 2.8 on a 100-point scale. Because of the bridge's design, it is considered "fracture critical" - there is no built-in redundancy to prevent the entire structure from collapsing if one component fails. In comparison, the I-35W Mississippi River bridge, another fracture critical bridge which collapsed on August 1, 2007, received a sufficiency rating of 50. [1]

These factors have led to consideration of either replacing the bridge or constructing a new one nearby. However, the National Park Service's policy requires the number of bridges on the river to remain constant, precluding an additional bridge. Local sentiment for the bridge is strong, backed by the bridge's status on the National Register of Historic Places, which makes the idea of a replacement very unpopular. Beginning August 1, 2005, the Minnesota Department of Transportation closed the bridge to perform substantial repairs at a cost of $5 million provided by Congress. The project includes renovating the Tender's House so that it would conform to modern safety standards while maintaining historical preservation.

On November 11, 2005, the bridge re-opened to traffic after the bridge deck had been replaced, ending a severe three-month traffic issue on the St. Croix.

The St. Croix River Crossing Project of MnDOT calls for the construction of a brand new, four-lane bridge less than a mile downriver, and converting the Stillwater Bridge to pedestrian and bicycle use.