SUMMIT COUNTY, Colo. (CBS4) – There was a celebration of the Eisenhower Tunnel this weekend marking 40 years of helping drivers get to and from the mountains.

The westbound bore of the tunnel first opened to traffic in March of 1973. Construction took five years.

The eastbound tunnel opened six years later. Since then more than 310 million vehicle trips have been made through the tunnels.

The Eisenhower helped lead to the development of both Summit and Eagle county ski areas.