Blue Water Bridge, Michigan

The only bridge over the St. Clair River is the Blue Water Bridge, which connects the communities of Port Huron, Michigan, and Sarnia, Ontario. The bridge is the second busiest commercial crossing between the two nations, after the Ambassador Bridge in Detroit. On the US side, the bridge is connected to two Interstates, 69 and 94, and is part of the trans-continental traffic flow between Chicago and Toronto, the Midwest and the Northeast. It is composed of two bridges, with traffic flowing one way over each span. The first bridge opened in 1938, originally with two lanes of traffic, one in each direction. A second bridge, on the south side of the first, opened in 1997. The international boundary is at the mid point of the spans. The bridge is more than a mile long, and is more than 150 feet over the river, to allow Great Lake freighter ships to pass underneath it. The expense of building such tall and large bridges is one reason that there are only four bridges between the Great Lakes of Huron, Michigan, Superior, and Erie, a region covering cities as far apart as Buffalo, Chicago, Sault Ste. Marie, and Duluth. North of the bridge, the international boundary enters Lake Huron.