1998 – Apple introduces the iMac computer.

1977 – The Big Ear, a radio telescope operated by Ohio State University as part of the SETI project, receives a radio signal from deep space; the event is named the "Wow! signal" from the notation made by a volunteer on the project.

1969 – The Woodstock Music & Art Fair opens in Bethel, New York, featuring some of the top rock musicians of the era.

1965 – The Beatles play to nearly 60,000 fans at Shea Stadium in New York City, an event later regarded as the birth of stadium rock.

1939 – The Wizard of Oz premieres at Grauman's Chinese Theater in Los Angeles, California.

2023 – Former U.S. president Donald Trump is charged in Georgia along with 18 others in attempting to overturn the results of the 2020 election in that state, his fourth indictment of 2023.

1935 – Franklin D. Roosevelt signs the Social Security Act, creating a government pension system for the retired.

1901 – The first claimed powered flight, by Gustave Whitehead in his Number 21.

1942 – Major General Eugene Reybold of the U.S. Army Corps of Engineers authorizes the construction of facilities that would house the "Development of Substitute Materials" project, better known as the Manhattan Project.

2017 - The Unite the Right rally occurs in Charlottesville, Virginia, leading to the deaths of 3 and injuring nearly 50 more.

1981 – The IBM Personal Computer is released.

1953 – First thermonuclear bomb test: The Soviet atomic bomb project continues with the detonation of "RDS-6s" (Joe 4) using a "layered" scheme.

1883 – The last quagga dies at the Natura Artis Magistra, a zoo in Amsterdam, Netherlands.

1984 – "We begin bombing in five minutes": United States President Ronald Reagan, while running for re-election, jokes while preparing to make his weekly Saturday address on National Public Radio.

1942 – Actress Hedy Lamarr and composer George Antheil receive a patent for a Frequency-hopping spread spectrum communication system that later became the basis for modern technologies in wireless telephones, two-way radio communications, and Wi-Fi.

1929 – Babe Ruth becomes the first baseball player to hit 500 home runs in his career with a home run at League Park in Cleveland, Ohio.

1974 – As a direct result of the Watergate scandal, Richard Nixon becomes the first President of the United States to resign from office. Vice President Gerald Ford becomes president.

1945 – World War II: Nagasaki is devastated when an atomic bomb, Fat Man, is dropped by the United States B-29 Bockscar. Thirty-five thousand people are killed outright, including 23,200–28,200 Japanese war workers, 2,000 Korean forced workers, and 150 Japanese soldiers.

1944 – The United States Forest Service and the Wartime Advertising Council release posters featuring Smokey Bear for the first time.

1854 – American Transcendentalist philosopher Henry David Thoreau publishes his memoir Walden.