The first atomic bomb was detonated at 5:29:45 am on July 16, 1945 at Alamagordo, New Mexico.

The Manhattan Project test.

Three weeks later on August 6, 1945 the first atomic bomb used in a war was dropped on Hiroshima, Japan. 66,000 people died and 4 1/2 square miles of the city was completely destroyed.

Three days later a second bomb was dropped, this time on Nagasaki, Japan. It killed 36,000 people and destroyed 40% of the city. Neither of these were the deadliest bombing attacks on Japan. Over 100,000 people died as a result of the Operation Meetinghouse bombing on Tokyo on March 9, 1945. The biggest difference is that the Tokyo bombing used 330 B-52s and they used incendiary bombs carrying napalm.

The dates of the first atomic bomb tests by other countries are:

USSR – August 29, 1949
United Kingdom – October 3, 1952
France – February 13, 1960
China – October 16, 1964
India – May 18, 1974
Israel – September 22, 1979…maybe
Pakistan – May 28, 1988
North Korea – October 9, 2006 but that one was a bit weak. They had a for realsies one on February 12, 2013

Time lapse map showing all of the nuclear explosions from 1945 through 1998 – that’s 2053 nuclear explosions.

Here’s the tl;dw version.

How atomic bombs work.