The Sioux Narrows Bridge is a bridge on Highway 71 at Sioux Narrows, Ontario, which spans the Sioux Narrows strait between Regina Bay and Whitefish Bay on Lake of the Woods. Built in 1936 as an all-wooden truss bridge made of Douglas fir timber treated with creosote, it was at 210 feet (64 m) the longest single-span wooden bridge in North America. The bridge overlooks the site of an 18th-century battle in which the local Anishnaabe and Cree nations defeated an invading force of Sioux. Due to its unique construction, the bridge was designated a heritage site under the Ontario Heritage Act.