September 30 is the 273rd day of the year (274th in leap years) in the Gregorian Calendar, with 92 days remaining, as the final day of September.
- 1399 - Henry IV is proclaimed King of England.
- 1452 - First printed book, the Johann Gutenberg Bible.
- 1867 - United States takes control of Midway Island.
- 1882 - The world's first hydroelectric power plant (later known as Appleton Edison Light Company) began operation on the Fox River in Appleton, Wisconsin.
- 1888 - Jack the Ripper kills his third and fourth victims, Elizabeth Stride and Catherine Eddowes.
- 1895 - Madagascar becomes a French protectorate.
- 1935 - The Hoover Dam is dedicated.
- 1935 - "The Adventures of Dick Tracy" first heard on the Mutual Radio Network.
- 1947 - World Series, featuring New York Yankees and the Brooklyn Dodgers, is televised for the first time.
- 1949 - Berlin Airlift ends.
- 1954 - The submarine USS Nautilus is commissioned as the first nuclear reactor powered vessel.
- 1960 - The last episode of "The Howdy Doody Show" airs on NBC.
- 1961 - Mayor Snyder of Oregon writes a check for $1.96 to cover the cost of the tea lost in the Boston Tea Party.
- 1962 - César Chávez founds the United Farm Workers.
- 1962 - James Meredith enters the University of Mississippi, defying segregation.
- 1965 - Civil unrest followed a failed c'oup attempt by Indonesia Communist Party (PKI). More than a million people died.
- 1966 - The British protectorate of Bechuanaland declares its independence, and becomes the Republic of Botswana.
- 1967 - Launch of BBC Radio 1; other national BBC radio stations also adopt numeric names.
- 1980 - Ethernet specifications published by Xerox working with Intel and Digital Equipment Corporation.
- 1982 - Cyanide-laced Tylenol kills six people in the Chicago, Illinois area. Seven were killed in all. The incident is known as the Tylenol scare.
- 1982 - The popular TV sitcom Cheers premieres.
- 1989 - Foreign Minister of West Germany Hans-Dietrich Genscher's speech from the balcony of the German embassy in Prague
- 1991 - President Jean-Bertrand Aristide of Haiti is forced from office.
- 1997 - Origin Systems Inc. releases Ultima Online, the first true massively multiplayer game, opening the door for a new video gaming genre.
- 1999 - Japan's worst nuclear accident at a uranium reprocessing facility in Tokai-mura, northeast of Tokyo, Japan. Workers overload a container with uranium, exposing workers and local residents to very high radiation levels.
- 1227 - Pope Nicholas IV (d. 1292)
- 1732 - Jacques Necker, french diplomat, finance minister of Louis XVI (d. 1804)
- 1800 - Decimus Burton, architect (d. 1881)
- 1882 - Hans Geiger, German physicist (d. 1945)
- 1895 - Lewis Milestone, Russian/American movie director (d. 1980)
- 1898 - Princess Charlotte of Monaco (d. 1977)
- 1904 - Waldo Williams, poet (d. 1971)
- 1913 - Bill Walsh, American movie producer and writer (d. 1975)
- 1917 - Park Chunghee, President of South Korea (d. 1979)
- 1917 - Buddy Rich, drummer (d.1987)
- 1921 - Deborah Kerr, actress
- 1924 - Truman Capote, author (d. 1984)
- 1928 - Elie Wiesel, Holocaust survivor, author, lecturer
- 1931 - Angie Dickinson, actress
- 1935 - Johnny Mathis, singer
- 1942 - Dewey Martin, drummer
- 1942 - Frankie Lymon, singer (d.1962)
- 1943 - Marilyn McCoo, singer
- 1947 - Marc Bolan, musician (d. 1977)
- 1954 - Barry Williams, actor, The Brady Bunch
- 1961 - Eric Stoltz, actor
- 1964 - Trey Anastasio, musician (Phish)
- 1972 - Ari Behn, Norwegian author
- 1980 - Martina Hingis, Swiss tennis player
September 29 - October 1 - August 30 - October 30 - more historical anniversaries
ca:30 de setembre
es:30 de septiembre
eo:30-a de septembro
oc:30 de setembre
pt:30 de Setembro
wa:30 di setimbe