Presidential succession refers to the procedure for replacing the president (or vice president) in the event of death or some other form of removal. The Constitution (text) (Article II, Section 1, Clause 6) stipulates that the Vice President is to replace the President, but grants to Congress the power to determine further succession.
A Presidential Succession Act of 1792 provided that after the Vice president, the next officials in line would be the President Pro Tempore (presiding officer) of the Senate and the Speaker of the House of Representatives.
American history has seen a continuing struggle between the executive and the legislature for dominance. During the Civil War, Abraham Lincoln had vastly strengthened the presidency, a fact deeply resented by many in Congress. The balance tipped the other direction under Andrew Johnson (unwillingly) and U.S. Grant (willingly), when the Radical Republicans gained influence. Respect for the presidency (and some accompanying power) returned under Rutherford Hayes and Chester Arthur.
The contest for dominance was complicated by the emergence of a newly empowered force in the 1880s — the American businessman. In this age, the Rockefellers and Carnegies were regarded by many as the elite. They were seen as superior to mere politicians who supped at the public trough. Businessmen, however, had to struggle and use their wits to survive — an affirmation of what was called "Social Darwinism."
This reverence for executives played a part in the passage of the Presidential Succession Act of 1886, which dropped the politicians (President Pro tempore and Speaker) from the line of succession and installed the Cabinet secretaries in the order in which their departments were created.