Click on The Bomb Timeline and a new window will pop up. You can move this to the side a bit 

Click on the dates prior to 1950 an answer the following questions in your notebook

Before the Cold War, what country, other than the Soviet Union, was the US competing against in the nuclear arms race?

Where  and when was the US's first atomic device detonated?

When did the US's monopoly on nuclear devices end?.

Close the window after you are done.