Within the federal government, the departments are among the oldest primary units of the executive branch, the Departments of State, War, and the Treasury all being established within a few weeks of each other in 1789. The heads of the departments are the members of the traditional Cabinet; since 1792, they have, by statutory specification, constituted a line of succession, after the Speaker of the House and the President pro tempore of the Senate, to the presidency in the event of a vacancy in both that office and the vice presidency. The Constitution is referring to these officials when it authorizes the President, in Article II, section 2, to "require the Opinion, in writing, of the principal Officer in each of the executive Departments, upon any Subject relating to the Duties of their respective Offices." In brief, they and their organizations are the administrative arms of the President.
All departments are listed by their present-day name and only departments with past or present cabinet-level status are listed.
| Department | Creation | Modifications since creation |
|---|---|---|
| State | 1789 | |
| War (past) | 1789 | Subsumed by Defense |
| Treasury | 1789 | |
| Navy (past) | 1798 | Subsumed by Defense |
| Interior | 1849 | |
| Justice | 1870 | |
| Post Office (past) | 1872 | Reorganized as U.S. Postal Service |
| Agriculture | 1889 | |
| Commerce | 1903 | Originally named Commerce and Labor; Labor later separated |
| Labor | 1913 | |
| Defense | 1947 | Initially named the National Military Establishment. |
| Health and Human Services | 1953 | Originally named Health, Education, and Welfare; Education later separated |
| Housing and Urban Development | 1965 | |
| Transportation | 1966 | |
| Energy | 1977 | |
| Education | 1979 | |
| Veterans Affairs | 1988 | |
| Homeland Security | 2002 |
Sources:
Relyea, Harold C. "Homeland Security: Department Organization and Management", Report for Congress. 2002. RL31493. http://fpc.state.gov/documents/organization/13385.pdf (August 7, 2002).
