The resource of potential oil represented by Green River Formation oil shale on Naval Oil Shale Reserve No. 1 (NOSR No. 1) in the southeast corner of Colorado's Piceance Creek Basin is evaluated in detail. NOSR No. 1 is the site of intensive long-term oil-shale development studies and is the source of innumerable oil-shale samples for all manner of testing. A brief history of these studies is presented. This oil-shale resource is defined from oil-yield assay data on 33 cores plotted as histograms and correlated into cross sections. Contour maps of thickness, richness and oil resource in place are presented for the Mahogany Zone, the rich zone in the Mahogany zone, and for 2 units beneath and 5 units above the Mahogany zone. Total oil shale resource on NOSR No. 1 is 20.4 billion barrels of which 17.4 billion barrels are particularly suitable for development by vertical modified in-place processes. A previously unknown Mahogany zone outcrop providing much additional development access is described. Now under sole control of the US Department of Energy (DOE), NOSR No. 1 offers DOE a unique site for oil shale testing and development.