- May 1 Charlie Robertson of Chicago pitches a perfect no-hit, no-run game
- May 2 WBAP-AM begins broadcasting from Fort Worth, Texas
- May 3 Mayor Hylan closes streets for building of Yankee Stadium
- May 3 Salt layer find at Winterswijk
- May 4 KNX-AM in Los Angeles CA begins radio transmissions
- May 5 Construction begins on Yankee Stadium (Bronx)
- May 7 Belgian soccer team defeats Netherlands: 1-2
- May 7 NY Giant Jesse Barnes no-hits Phillies, 2-0
Event of Interest
May 9 The International Astronomical Union formally adopt Annie Jump Cannon's stellar classification system, which with only minor changes, is still used today
Annie Jump Cannon
- May 10 Dr Ivy Williams is 1st woman to be called to the English Bar
- May 10 WHB-AM in Kansas City MO begins radio transmissions
- May 10 The United States annexes the Kingman Reef in n the North Pacific Ocean
- May 13 48th Kentucky Derby: Albert Johnson aboard Morvich wins in 2:04.6
- May 13 47th Preakness: L Morris aboard Pillory wins in 1:51.6
- May 15 Germany turns over the Upper Silesia region to Poland under Allied pressure and despite a plebiscite in favor of merging with Germany
- May 16 White Star Liner Majestic completes 5½ day maiden voyage
- May 18 Dutch 2nd Chamber agrees to 48 hour work week (was 45 hrs)
- May 20 "Egypt" sinks off Ushant after colliding with "Seine" killing 90
- May 21 "On the Road to Moscow" is 1st cartoon to receive a Pulitzer Prize
- May 21 Col Ruppert buys out Col Huston interest in NY Yankees for $1,500,000
- May 21 Pulitzer prize awarded to Eugene O'Neill for his play "Anna Christie"
- May 21 Ruppert buys out Huston interest in Yankees for $15 million
- May 23 "Abie's Irish Rose" 1st of over 2,500 performances
- May 23 Harry Greb gives Gene Tunney his only professional boxing defeat
Event of Interest
May 23 Walt Disney incorporates his 1st film company Laugh-O-Gram Films
Walt Disney
Event of Interest
May 26 Vladimir Lenin suffers a stroke
Vladimir Lenin
- May 29 Ecuador becomes independent
- May 29 US Supreme Court rules organized baseball is a sport and not a business and thus not subject to antitrust laws
- May 30 Latvia & Vatican sign accord
- May 30 Completed Lincoln Memorial dedicated by US Chief Justice William H. Taft in front of 50,000
- May 30 Cubs swap Max Flack for Cards Cliff Heathcote during middle of doubleheader. Both play for both teams that day
- May 30 Indianapolis 500: Jimmy Murphy wins in 5:17:30.845 (152.057 km/h)