State Street at Christmastime looking north towards the capital December 7, 1948. Courtesy of the University of Utah, Marriott Library. 

Like other urban centers across the nation, postwar growth in Salt Lake City saw its downtown streets become increasingly crowded. In 1947, a comprehensive “origin   and destination” traffic study was conducted in the Salt Lake Metropolitan Area.

This traffic study determined that 85 to 95 percent of traffic used the State Street portion of Highway 89 to enter Salt Lake City.  Traffic from the highway, the main   north-south route in the area, had become too much for downtown to bear.   Something needed to be done.[1]