This paper examines the U.S. government’s intramural research and development efforts over a 40-year period, drawing together multiple human capital, government spending, and patent datasets. The U.S. Federal Government innovates along four dimensions: technological, organizational, regulatory, and policy. After discussing these dimensions, the paper focuses on the inputs to and outputs of government intramural technological innovation. We measure innovative effort and results by accounting for the government scientists and dollars committed to R&D and patents created with government involvement. Overall, we show that intramural innovations, measured by government-assigned patents, are slightly more original and general, but less cited, than patents awarded to private-sector companies and extramural organizations patenting in the same technology classes. The majority of the 200,000 federal government scientists work at the Department of Defense, the Department of Energy, and NASA, and are largely in physical science and engineering occupations; the scientific expertise of other agencies is heavily weighted toward mathematics, social sciences, and data analytics. As these latter disciplines’ innovative outputs are less readily catalogued with patents, measuring total government innovative output with government-assigned patents is likely to over-emphasize innovations in engineering and physical sciences while under-reporting intramural innovations in other disciplines. We discuss the implications of our findings for both public- and private-sector innovation efforts and pose questions for future research.