The primary role of the Speaker of the House is to preside over the House of Representatives. The speaker is chosen by majority vote of that body, usually along strictly partisan lines.
For many years, the speaker was an extremely powerful figure, especially during the later 19th and early 20th centuries. Holders of the office exerted great influence through their power to appoint House members to committees and by their seat on the Rules Committee, where they shaped the House agenda and framed the later debates.
Republican Thomas B. Reed of Maine earned the nickname Czar Reed during the 1889-1891 session, when he heavy-handedly increased the speakers powers. Insurgent Republicans and Democrats joined forces in 1890 to tame Reed.
Another powerful speaker, Republican Joseph G. Cannon of Illinois, was perhaps the most dictatorial of all. He served in Congress for nearly 50 years, but the height of his influence occurred during the administrations of Theodore Roosevelt and William Howard Taft. Uncle Joe, as he was called, routinely and unilaterally halted much progressive legislation. The Revolution of 1910 saw Cannon's and subsequent speakers' powers diminish; notably his removal from the Rules Committee and reduced capacity to make committee appointments.
During the 1970s, further reform of the office was made under a movement to modify the seniority rules for the House.
Today the speaker remains one of the most potent political figures in Washington. He has the power to make appointments to special committees and can doom bills with his authority over scheduling floor debates. The speaker is also responsible for assigning bills to committee and sometimes makes a selection based upon his belief that a particular committee chairman will either promote or kill the bill.