It's impossible to know immediately what's most important when the Kennedy Presidential Library decides to go online - but I can tell what I found most historic and electrifying.
It's the recordings made of President John F. Kennedy as he sorted out the prospect of nuclear war with the Soviet Union during the Cuban Missile Crisis of October, 1962, and he calls to consult with former President Dwight D. Eisenhower.
My favorite high stakes Eisenhower consultation is here starting at about 5:05 into the clip.
Imagine having to decide in real time, when you cannot be wrong, what move might lead to all out war. At this point in the crisis, the U.S. had demanded that the Soviets remove the missiles they had installed (and tried to hide) in Cuba, all of which were aimed at the U.S. The Russians were publicly denying the silos contained missiles.
Kennedy knew he wasn't backing down. In fact, he was planning both a blockade and invasion of Cuba.
The Navy and Army were mobilizing and assembling ships and personnel. What he didn't know was the point at which he would provoke the Soviet leader, Nikita Khrushchev.
It's clear this was no mere courtesy call from a sitting President to his predecessor.
This was a young President picking the strategic brain of a man who knew the Russians - both as a former President and as Allied Commander in World War II.
This phone call and others drives a moment of history home, and has to rank among the most dramatic decision point moments ever captured on tape.