NIH expenditures are reported according to the "mechanism" of support. Description of these mechanisms (e.g. grant, R&D contract, intramural, etc.), a brief overview of NIH, and tables detailing expenditures from Fiscal Year 1983 to the present, can be found here: Spending History by Institute/Center, Mechanism, etc. (1983 to present).
NIH received its first appropriation in 1938, for the National Cancer Institute. We now receive 26 separate appropriations for our NIH components. You may view the entire history of NIH appropriations: Appropriations History by Institute/Center (1938 to present).