This month marks the 40th anniversary of the opening and dedication of the westbound Eisenhower Tunnel bore, the highest facility of its kind in the world.
Construction on the first of the two bores was completed in 1973.
The 1.7-mile facility allowed drivers to avoid the 9.5-mile trek over Loveland Pass. Traffic traveling in both directions used the first bore until the eastbound side - known as the Johnson Tunnel - was completed in December 1979.
"The Eisenhower Tunnel ushered in a new era of accessibility between the two sides of Colorado and changed the way we perceive Colorado, uniting east and west slopes with a new spirit of common purpose," Colorado Department of Transportation chief Don Hunt stated in a release on the anniversary. "The tunnels provided reliable customer access that helped lead to the development of international-level ski resorts."
Today, more than 310 million vehicles have passed through the Eisenhower/Johnson memorial tunnels.