Federal administrative agencies have been a critical part of our political process for over 100 years, but their role in our government has changed considerably over that period of time.
When the American republic was young, the executive branch of the government was small. The first agencies of the federal government were the Departments of War, State, Navy, and Treasury. There was also an Office of the Attorney General.
The growth of the country and the expansion of governmental responsibilities led to the creation of the Department of the Interior in 1849, the Department of Justice in 1870, and the Post Office Department in 1872.