Regional bus service came to the Eagle Valley in 1980, funded by Vail Associates. The initial bus service was designed primarily to transport skiers between Beaver Creek and Vail Mountain but also to carry employees between Edwards and Vail.  It brought workers residing in Leadville to the valley. In the mid-eighties, Eagle County operated the regional bus service by way of contract with various transportation providers. In the winter of 1987-88, the town of Avon took over the operation of the regional bus service and continued operation through  intergovernmental agreements until April 2001, when ECO Transit officially assumed day-to-day operations for regional bus service.

In the early years (1987-88) the regional bus service was funded by farebox revenues and through subsidies from the towns of Vail and Avon, Beaver Creek Resort and Eagle County. At this time, regional bus service was limited to early morning and late afternoon employee routes including a Leadville run and a skier shuttle that operated ten hours per day. This was a bare bones approach to keep operating costs low.

The funding partners decided in 1994 to seek a dedicated funding source (Eagle County transportation sales tax) for regional transportation. As the valley's population had grown, the demands for transportation had also increased, and this translated into a larger financial commitment from the funding partners. A ballot initiative for a dedicated funding source was approved by the voters in November 1995. The Eagle County Regional Transportation Authority was made official on January 1, 1996.

A nine member board of elected officials from the incorporated towns was established to develop operating policy. This board has since been reduced to eight members who represent the towns of Red Cliff, Minturn, Vail, Avon,  Eagle, Gypsum, Eagle County Government and Beaver Creek. The half-cent county sales tax is dedicated to funding regional transportation.  One-tenth of this tax goes toward funding the regional trails system.

In 2001, Eagle County completed construction of the Gypsum Maintenance Facility shared by ECO Transit, the county's Road & Bridge and Motor Pool Departments. This facility houses ECO’s administrative, marketing, operations and fleet maintenance functions. Today ECO supports an operating staff of approximately 60 with a budget of around seven million dollars.