Rainbow Bridge ended the dangers of the Donner grade on California’s state highway system at a time when automobile travel over Donner Summit had been difficult and harrowing. The old route of the Lincoln Highway can still be traced in the dirt sections on the hill. As auto travel grew in popularity in the 1920’s and travelers demanded better roads, the U.S. Forest Service undertook improvements to transportation up to Donner Pass in order to move lumber out of the Tahoe Basin, where grades on Donner Summit sometimes reached 18 percent and hindered transit. The Forest Service contracted for Rainbow Bridge, a giant highway engineering feat that required two years of constant work and became the first bridge with a grand and compound curve. Completed for $37,304.32, it improved lumber transport and also brought more people to Donner Summit and Lake Tahoe. Rainbow Bridge was later featured in films, television commercials, and print advertisements, and in the summer of 2007 a bear climbed into its supports, was tranquilized, and removed.