Tell and Theo Ertl purchased the Eldora Ski Area in 1967. The previous winter, Eldora had been open for 28 days. Dr. Ertl installed a snowmaking system, introduced night skiing, and built five chair lifts. By 1975, the ski area attracted 150,000 skiers, and employed as many as 200 people. In the 1970’s, Tell and Theo were instrumental in the reclamation of gravel pits on their property east of Boulder, creating a wildlife habitat area. Since Tell’s death, Theo continues her activities with non-profit organizations.