The second of NASA's 'Great Observatories', the Compton Gamma Ray Observatory (CGRO) was one of NASA's most successful missions. The scientific results changed our view of the hig-energy Universe in many fundamental ways. Originally designed as a two-year mission, CGRO continued to return hgih quality scientific data until a reference-gyro failure led NASA to de-orbit the spaceraft after nine years of operations while the capability for a controlled reentry remained. Success is a result of careful planning and wise leadership. It is useful to examine how such a mission was designed, developed, and implemented, as a model for future scientific missions. Careful scientific planning, a highly skilled and motivated project staff who worked closely with the scientists, a close working relationship with TRW, the mission contractor, a dedicated operations crew and strong support from the management of the Goddard Space Flight Center were all important to the success of CGRO. It is the purpose of this paper to examine CGRO activities from the initial science planning beginning in the eraly 1970's to the end of mission funding in 2002 to see what can be learned from the successes and the failures of this grand mission.