The Donner Memorial Bridge, also referred to as the Rainbow Bridge, is a concrete arch span built during the 1920s near Donner Summit. The bridge was part of historic US Route 40, the primary east-west highway for motorists traveling between San Francisco, CA and Atlantic City, NJ until Interstate 80 was constructed in 1964. The bridge provides beautiful views of Donner Lake, the Town of Truckee and the surrounding area of Donner Summit. Many visitors stop to take pictures and admire the view. Rainbow Bridge has also been used in commercials and as a prop in movies, including "True Lies."
Prior to construction of the Rainbow Bridge, old Highway 40 wound steeply down Donner Summit with grades as high as 18%. Automobiles were increasingly used in the area, and as the demand for better roads grew, the decision to create the bridge was made.
Rainbow Bridge was a common design for the 1920’s. Other bridges with similar designs were constructed at Yuba Gap, Big Sur, Redding, and Folsom. Rainbow was unique because of its placement: it was on a grade, and had a compound curve that had never been attempted before. The final 1925 construction report says, “The alignment consists of a series of compound curves; there being a 360 foot radius curve over the arch and a 145 ft radius over each approach span.”
The gravel and sand that made up the concrete for the bridge was mined at Donner Lake and mixed on site. The proposed cost for the bridge was $26,000, but it ended up costing $37,304.32 when it was completed in 1926, due to design changes and additions. The final cost gave the contractor a profit of about $1,319.
Decades of heavy use in a harsh climate caused the Rainbow Bridge to deteriorate. When I-80 was completed in 1964, Old 40 was given to Nevada County. By the early 1990s, Nevada County needed to take action to solve the deterioration. They considered tearing it down, but the Donner Summit community pushed to save the bridge. The community helped with fundraisers, letter writing, and attending hearings. A grant was written to the State of California by Steve Beucus, the Donner Summit Public Utility District general manager at that time. The grant was approved, and the County Board of Supervisors became interested in saving the Rainbow Bridge also. The County kicked in $1.6 million, and the bridge was restored in 1993. The replacement concrete was color matched so the rehabilitated bridge would look identical to the old. The only change was that the openings in the railings were made smaller so that people’s heads could not get stuck.