Alamogordo is a place in the state of New Mexico, USA. It's a small town with lots of hot sun and big, sandy desert.
A long time ago, in the 1940s, the United States government built something called a "test site" there. They wanted to test really powerful bombs and rockets to see if they would work, because they were worried that other countries might have bombs too.
So they tested these bomb and rocket things in Alamogordo, and it made a really big explosion! It was so big that it made a white cloud in the sky that was taller than a big building. This explosion was called "Trinity" and it was really important because it showed that the United States was really powerful with these bombs.
But, some people didn't like that the government was testing nuclear bombs near their homes, and they were worried that it might hurt people or make them sick. So, after a while, the government stopped doing tests in Alamogordo.
Now, Alamogordo is a place where lots of people live, and there are still some places where you can see the remains of the old test site. People still remember what happened there, and they are careful to make sure that nothing like that ever happens again.