The 1,500m-long extradosed bridge will carry four lanes of traffic in each direction over the St Croix River between the city of Oak Park Heights in Minnesota and the town of St Joseph in Wisconsin.

St Croix Crossing

The bridge has been designed to fit into the river gorge as naturally as possible. Use of the hybrid design - a combination of a cable-stayed and segmented concrete box structure - ensured that the pier heights, which reach 20m above the bridge surface, would not be higher than the bluffs along the river.

The departments of transportation of the two states opened the bridge to traffic following the dedication ceremony, which took place on Wednesday.

The St Croix Crossing replaces the Stillwater Lift Bridge, which was dedicated more than 80 years ago. Over the years, as traffic increased, travellers faced mounting congestion because the bridge periodically needs to lift to accommodate boat traffic on the St. Croix River.

The new bridge, about a mile downstream from the Lift Bridge, is designed to carry more than twice the 18,000 vehicles a day that now cross the river. The St Croix Crossing is 30.5m wide and stands between about 33m and 45m above the water, allowing boat traffic to freely move beneath it.

The superstructure has been built by Lunda/Ames Joint Venture and the design was by HDR, working with Buckland & Taylor (which is now Cowi North America).