Oil shale resources in the United States are important as an alternative energy source. The reserve in the Green River Formation is by far the largest known petroleum resource in the world. Knowledge of the mechanical properties is essential to any form of development, including the environmentally acceptable in-situ processes. This paper emphasizes the creep behavior of oil shale samples taken from the Parachute Creek Member of the Green River Formation. A nonlinear rheological model was developed for the creep behavior. Other mechanical properties, including 3-D stiffness on rich, medium, and lean oil shale's are presented. It was concluded that the organic content and the stress levels were important parameters. Effects of mineral logy and geological aspects are also discussed, and these appear to have some influence on the mechanical properties of oil shale. Lacustrine depositional environment in four principal basins (Uinta Basin of Utah, Perchance Basin of Colorado, Green River and Washakie Basin of Wyoming) and their extreme horizontal uniformity are presented. The mineral dolomite provides a structure to the carbonate oil shale, strongly modifying the effect of organic volume changes. The greatest influence on fracturing and some jointing depends on the mineralogical content, the minor tectonic situation, and the organic content.