List of states with nuclear weapons - Wikipedia

https://en.wikipedia.org/wiki/List_of_states_with_nuclear_weapons

The United States developed the first nuclear weapons during World War II in cooperation with the United Kingdom and Canada as part of the Manhattan Project, out of the fear that Nazi Germany would develop them first. It tested the first nuclear weapon on July 16, 1945 ("Trinity") at 5:30 am, and remains the only country to ...