When the founders of the United States gathered to create the foundations of the country, they decided on three branches of government, with a president central to the executive branch. Kenneth C. Davis explains why this decision was not necessarily inevitable and what variables were up for debate.
You can read more about the history of the presidency and the individual Presidents in Don’t Know Much About® the American Presidents by Kenneth C. Davis.
Here are more places to learn about presidential powers:
Exploring Constitutional Law: The University of Missouri-Kansas City Law School
The Miller Center, University of Virginia