Selection of encyclopedias dealing with political rhetoric. Many include sample speeches.
Public Papers of the Presidents of the United States currently contains the papers and speeches covering the administrations of Presidents Hoover, Roosevelt, Truman, Eisenhower, Kennedy, Johnson, Nixon, Ford, Carter, Reagan, Bush, and Clinton. For more recent administrations see the Compilation of Presidential Documents. Also see Inaugural Addresses of the Presidents of the United States (currently through Trump). Many presidential libraries also include speeches & remarks.