The North Park, South Park, and the Raton Basins of Colorado were formed in the compressive environment of the Late Cretaceous-Early Tertiary Laramide Orogeny (70-35Ma.). The Pennsylvanian-Permian Ancestral Rocky Mountains (~240-280Ma) and Neogene (~33Ma) extension in southern Colorado has also affected some of these basins. The purpose of this study is to determine the structure and origin of these basins and integrate the results with other studies carried out by the CD-ROM (Continental Dynamics-Rocky Mountain) project. A series of filtered (smoothed and bandpassed) gravity maps and computer models (2.5-D) have been created for the different basins. Results indicate that the gravity low over North Park is the result of basin fill. The regional gravity low over northern South Park is attributed to the Colorado Mineral Belt while south South Park consists of two sub-basins separated by a structural high. South Park is bounded on the east by the Elkhorn Thrust fault that shows on the maps as a region with a high gravity gradient. Both the Raton and the North Park basins are asymmetrical and synclinal. The Raton basin is the easternmost of the Laramide age basins. Work in progress includes spatial analysis of the various data that will be used to further clarify the structure and origin of these basins. Methods being employed include overlays of gravity contours over topography using a DEM. TM images will also be used in the construction of other overlays.