On April 12, 1945, President Roosevelt died of a cerebral hemorrhage. Harry S Truman took the Oath of Office at 7:09 p.m., becoming President of the United States.

“I felt like the moon, the stars, and all the planets had fallen on me.”

Following the Oath, Henry Stimson, Secretary of War, lingered to speak with him about an “immense project.” Truman deferred an in-depth discussion to a later date.

Stimson pressed for an appointment on April 24, and Truman met with him the next day. This letter is on display at the Harry S Truman Presidential Library in Independence, MO.

For more info, see Harry Truman and the Bomb at the National Archives.