- Apr 3 KQW-AM in San Francisco CA changes call letters to KCBS
- Apr 3 WLWS (now WCMH) TV channel 4 in Columbus, OH (NBC) begins broadcasting
- Apr 4 Israel & Jordan sign armistice agreement
- Apr 4 North Atlantic Treaty Organization (NATO) treaty signed in Washington, D.C.
- Apr 4 WKRC TV channel 12 in Cincinnati, OH (ABC) begins broadcasting
- Apr 5 60 year old St Anthony's Hospital in Effingham, Illinois, catches fire, killing 77 people
- Apr 5 Fireside Theater debuts on US television.
South Pacific
Apr 7 Richard Rodgers and Oscar Hammerstein's musical "South Pacific", starring Ezio Pinza and Mary Martin opens at Majestic Theater, NYC; runs for 1928 performances and wins 10 Tony Awards
- Apr 9 Revival of Sidney Howard's Pulitzer Prize-winning 1924 stage drama "They Knew What They Wanted", closes at the Music Box Theatre, NYC, after 61 performances
- Apr 9 UN International Court of Justice holds Albania responsible for incidents in Corfu Channel and awards Britain damages
13th US Masters
Apr 10 13th US Masters Tournament, Augusta National GC: Sam Snead wins his first of 3 green jackets by 3 strokes over Johnny Bulla and Lloyd Mangrum
- Apr 13 Basketball Association of America Finals: Minneapolis Lakers beat Washington Capitols, 77-56 to take series, 4 games to 2; BAA and National Basketball League merge later that year to create the NBA
- Apr 13 Philip S. Hench at Mayo Clinc announces discovery of cortisone to treat rheumatoid arthritis
- Apr 14 International Military Tribunal at Nuremberg's last judgment
Shoemaker's First Win
Apr 20 Jockey Bill Shoemaker wins his 1st race, in Albany, California
Event of Interest
Apr 25 Friedrich Durrenmatt's "Romulus der Grosse" premieres in Basel
Admirals
Aviators
Gangsters
Generals
Industrialists
Suffragists