The development of an oil shale industry has had its ups and downs throughout this century. Despite vast reserves of recoverable shale oil, energy prices usually have been high enough to make extraction of that oil commercially viable. The tripling and then tripling again of world oil prices in the 1970s gave initial promise that development had become economically feasible. After only a few years of rapid development activity, however, the effort was brought to a near-halt by falling world oil prices. The results were a substantial reduction in economic activity for northwestern Colorado and, maybe more importantly, sharply lower expectations for the region's future economic growth. In both the upturn and the downturn, the local public sector was essentially shielded from financial stress because the energy companies helped fund public spending on infrastructure and services. The future for oil shale remains uncertain. A few energy companies continue to pursue their development plans. To spur development of commercial scale plants, Synthetic Fuels Corporation has made loan and price guarantees to energy firms. Some projects may soon be extracting oil, providing needed technological and financial information on various techniques of oil extraction. But the future for oil shale remains clouded by uncertainties regarding the cost of producing syncrude and future oil prices. Environmental issues could also hamper oil shale development. Therefore, oil shale remains, as it has for more than a century, a technical and economic enigma that has only begun to be understood and developed. 8 references, 3 figures, 3 tables