- Lobbyists--United States.2
- Lodge, Henry Cabot, 1850-1924.2
- Longworth, Alice Roosevelt, 1884-1980.2
- MacDonald, James Ramsay, 1866-1937.2
- Machado y Morales, Gerardo, 1871-1939.2
- Mail.2
- Manners and customs--United States.2
- Marching bands.2
- Martin airplanes.2
- Mayflower (Yacht)2
- Mayo, Charles Horace, 1865-1939.2
- Mayors.2
- McKellar, Kenneth Douglas, 1869-1957.2
- Meetings.2
- Memorial rites and ceremonies.2
- Men.2
- Metal castings.2
- Military art and science.2
- Mitchell, William D. (William De Witt), 1874-1955.2
- Money supply.2