The Postmaster General of the United States is the head of the United States Postal Service. The position has changed roles over the years. The Post Office was created even before the Declaration of Independence, and Benjamin Franklin was the first Postmaster General. He was also the last person to serve in the position whose name would be familiar. Up until 1970, the Postmaster General was in charge of a government department, and for most of that time was a member of the cabinet. Although running the post office would presumably take a great amount of managerial skill, it probably dealt with much less weighty problems than say, Defense or State. The cabinet-level position was instead used to reward key supporters of the President.
All of this changed in 1971 when the Post Office Department was rechartered as an autonomous public corporation. The position of Postmaster General became even less political, since the Post Office was now ran more like a business than an executive department. The Postmaster General became if anything more anonymous, with almost all holders of the office being anonymous functionaries, despite being in charge of what is one of the largest businesses in the country.