Bridges were among last items completed on Alaska Highway
The Johnson River Bridge, at Mile 1380 of the Alaska Highway, was constructed in 1944
The dedication of the Alaska Highway on Nov. 20, 1942, received great publicity. However, stories often paid scant attention to the actual condition of the road when it first began accepting through traffic. The public could be forgiven for thinking that the highway was finished, essentially ready for any traffic the U.S. military and civilian population could send over it.
Janet Haigh’s book, “The Alaska Highway,” relates that by the end of 1942 the Alaska Highway was actually little more than a rough track winding through the wilderness. The road was narrow and often winding, with corduroyed sections (gravel-covered wood poles laid across the road bed) through marshy areas, and overly steep grades in other places. Wooden culverts and simple timber-bridges forded small creeks. Larger piling- or timber-trestle bridges, as well as ferries, were used to cross bigger streams and rivers.
The road was only passable by vehicles with high ground clearance and preferably 4- or 6-wheel drive. In the summer, vehicles had to navigate muddy roads that were prone to washout. Winter brought its own problems, with mechanical problems caused by sub-zero temperatures, and road sections that repeatedly flooded with overflow and became encased in multiple layers of ice.
According to K.S. Coats and W.R. Morrison’s book, “The Alaska Highway in World War II,” when Canada and the United States signed the agreement allowing the U.S to build the highway across Canadian territory, the initial goal was to build a road “to a standard sufficient only for the supply of troops engaged in the work.” The road was built to minimum military standards, and military convoys were the primary users — capable of navigating the rough road, and able to rescue anyone who had trouble along the way.
The agreement further stipulated that the highway would be completed to civilian highway standards by 1943. This included widening the road, installing concrete culverts, and replacing most of the wooden bridges with steel ones.
The U.S. Public Roads Administration (PRA), which had toiled alongside the U.S. military to construct the initial road, assumed responsibility for its completion after November 1942. The PRA faced a monumental task. The spring thaw in 1943 undid much of the work accomplished the previous year.
With no experience in building roads in permafrost areas, insulating vegetation was often scraped from the ground during initial roadbed construction. This exposed the permafrost to thawing and resulted in sections of road that turned to quagmires the next summer. The PRA and its civilian contractors ended up rebuilding most of the highway.
Civilian engineers also determined that much of the route punched through by the military was unsatisfactory. Eventually, 67 percent of the road was rerouted, sometimes up to 10 miles away from the original route. By the end of 1943 the PRA had completed most of it highway improvements, except for bridge replacement.
To speed bridge construction, the PRA used standardized designs wherever possible. Warren trusses (named for James Warren, who, along with Willoughby Monzani, patented the truss in 1848) were used in many of the bridges. Bridge components were fabricated in the Lower 48 states and then shipped north.
The PRA used Warren trusses 200-feet long and 241/2-feet long. Short bridges used a single truss. For longer bridges additional trusses were added. One of the longest World War II era bridges along the Alaska Highway is the Gerstle River Bridge just south of Delta Junction, which has nine segments.
The bridge shown in the drawing is the Johnson River Bridge, at Mile 1380 of the Alaska Highway, 66 miles northwest of Tok. Composed of five Warren trusses, it’s length is listed at 9741/2 feet.
The Johnson River Bridge, along with most of the PRA’s steel bridge replacements, was completed by 1944. Only a handful these World War II era bridges remain along the entire Alaska Highway, four of them in Alaska.
Sources:
- “The Alaska highway: A Historic Photographic Journey.” Janet Haigh. Wolf Creek books. 2001
- “The Alaska Highway in World War II: The U.S. Army of occupation in Canada’s Northwest.” K.S Coates & W. R Morrison. University of Oklahoma Press. 1992.
