How has the executive branch changed since its inception?

Perhaps the most important change in the executive branch
since its inception has been the huge growth of the federal
bureaucracy.

When George Washington was the first president
under the new Constitution, the federal bureaucracy consisted of a few hundred people. 
There were only three cabinet level departments.  Nowadays, the federal government
employs over 2.5 million people.  Of course, the country is much bigger than it was in
those days.  However, the population now is only about 100 times bigger than it was in
those days and the increase in the bureaucracy has been much greater than
that.

The major change then, is that there is a much bigger
bureaucracy that gives the executive branch much more of a role in creating and
executing policies than it originally had.