Built in 1916-1918 and so named for the Scottish immigrant, local settler, and Skagit County Commissioner who promoted its construction. The naming occurred after Henry Thompson was killed by a logging train in 1918. At the time, its graceful arch was the longest single-span reinforced concrete bridge in the world and has been listed on the Washington State and National Historic Register since 1976. Until 1972, when the Washington State Department of Transportation re-routed Highway 20 (then known as Star Route 20) outside the town, the Thompson Bridge was the only connecting thoroughfare across the Baker River and into eastern Skagit County.
It underwent a complete rehabilitation in 2003-2004.