Park City and I-80

When we first moved to Park City, for four years, I was commuting every day on I-80 (Interstate 80) to Salt Lake City. I only traveled on the sole and previous road, Route 40, in 1971, but was asleep and didn’t remember a thing. 

Then, in 1980, I drove from Salt Lake to Park City on I-80 in 1980, but didn’t know how that impressive stretch of Interstate highway came to life. After doing some research. I found that I-80 was finally completed in the SLC airport area on August 22, 1986, while the specific stretch I knew so well between Salt Lake City and Kimball Junction (Park City) had been completed in 1973.

At that point, the entire 2,907-mile I-80 (from San Francisco to New Jersey) became the world’s longest completed freeway, and Salt Lake City became the "Golden Spike" of the Interstate Era. The transformation of the old two-lane US-40 into the mostly six-lane I-80 was one of the most difficult engineering feats in Utah's highway history due to the narrow, vertical walls of Parley's Canyon. The timeline of completion that follows speaks volumes about the work required that spanned from 1962 to 1973. 

• 1850: Parley P. Pratt completed the "Golden Pass Toll Road", marking the first time wagons could bypass the much steeper Emigration Canyon. 
• Late 1950s: With the passage of the Federal-Aid Highway Act of 1956, plans began to upgrade US-40 into a controlled-access freeway. 
• 1962: The section from Wanship to Silver Creek opened, which provided the first major "freeway" feel east of Kimball Junction. 
• 1969–1970 (The Big Closure): The most disruptive phase. A 5.5-mile section of Parley’s Canyon was completely closed to traffic for 9 months (October 1, 1969, to July 23, 1970). Drivers had to detour through Emigration Canyon or Weber Canyon to reach Park City. 
• 1971: The westbound lanes of the canyon stretch were officially opened in July, completing the four-lane "split" through the lower canyon. 
• 1973: The final segment between Mountain Dell Reservoir and Kimball Junction was completed, officially linking the Salt Lake Valley to Park City with a high-speed divided highway. 

Building a modern freeway through a narrow mountain corridor presented obstacles that required "brute force" engineering, like massive rock blasting. To fit six lanes of traffic into the lower canyon, engineers had to use millions of pounds of dynamite to blast away the sheer quartzite and limestone cliffs. 

This is why there are dramatic vertical rock cuts today near the mouth of the canyon. The thing that always amazed me was that the highway was essentially built "on top" of the creek in its lower section, with massive culverts installed and multiple shifting of water paths multiple times to make room for the roadbed. 

Managing the steep ascent to Parley's Summit (6% grade to reach from 4,610 to 7,120 feet) was a major concern for heavy trucks. Designing "runaway truck ramps" and the wide, sweeping curves was also essential to prevent the high-speed accidents that plagued the old US-40. 

Construction in 1967 near the mouth of the canyon required massive amounts of "fill" dirt, which nearly buried the local landmark known as Suicide Rock (it now sits much lower relative to the freeway than it did originally). 

Because the summit is over 7,000 feet, crews could only work effectively for a few months a year. Sudden mountain snowstorms frequently shut down construction and destroyed fresh roadwork, but in the end, it contributed to make Park City the world's most accessible ski town from an international airport!