1939-1945. U.S. involvement was from the time of the attack on Pearl Harbor, December 7, 1941 until the end of the war in 1945.
1939 to 1945.
World War 2 began when Japan invaded China in 1933. It ended in 1945 when Japan surrendered.
it was around the Great Depression in 1941-1945
Please see the related question.