January 10-15                    radical coup in Germany is suppressed

January 15                         molasses explosion (a 50-ft.-tall tank holding 2.3 M gallons) kills 21, injures 150 
in Boston. You might wonder how molasses can kill someone. Fortunately, a team from Harvard recently studied this: apparently the molasses had been heated to make it less viscous and easier to move, and it remained warm. When the tank exploded, the molasses rushed through the streets at 35mph, then quickly cooled, drowning people who had not been swept under by the first wave. Kind of the worst of both worlds. Detailed picture of the explosion.

February                             Allies secretly agree to 
intervene in USSR to overthrow nascent Soviet Union (some of your League of Nations debates mention this)

February 6-11                    
Seattle general strike

April                              more than 35 dynamite-filled bombs are mailed to politicians, newspapermen, and big-business figures but are intercepted before reaching them

June 2                                8 more anarchist bombings, this time successful, killing one. The house of Attorney General A. Mitchell Palmer is destroyed. FDR, then Assistant Secretary of the Navy, lived across the street and had walked by the house just before the explosion. (Their most successful attack 
hits Wall Street Sep. 16, 1920, killing 39.)

June 4                                 19th Amendment is sent to states, eventually giving women the vote (officially ratified Aug. 1920)

June 28                               German delegates and Allies sign 
Treaty of Versailles

July 27                                Chicago race riots 

August-Sept 25                  Wilson's whistle-stop tour of US to convince the American people that the Senate should ratify the Treaty and have the US join the League; Wilson collapses, ending the tour

September 9-13                  Boston police strike

September 21                     nationwide steel strike begins (final unions give up, 1920).
The image below is in English, Russian, Italian, Polish, Albanian, Croatian, Czech (fun fact: Czech sci-fi writer Karel Capek used his native word for labor, "robota," to coin the word "robot" in a 1920 play called Rossum's Universal Robots), and Hungarian.

October                               Chicago "Black Sox" throw World Series

October 28                          Volstead Act is ratified over Wilson's veto, beginning Prohibition

November 19                      Senate rejects Treaty of Versailles and League of Nations (info on the debate at bottom of this timeline)