By the time America elected Barack Obama, this historian would see, it was already on the way down.
Were he to simultaneously examine the rise of the welfare state, he would notice a telltale trend: As socialism dug deeper into the soul of America, America's pioneering spirit waned.
Americans stopped wanting to open new frontiers -- to get there first. Rather than take bold risks and settle new realms, Americans had settled down to wait for the government's largesse.
Fifty years ago last week, a Democratic president gave a speech to a joint session of Congress in which he expressed a different view. In that speech, John F. Kennedy called for Americans to send a man to the moon and bring him back within the 1960s, and to do so not only as an expression of the superiority of freedom over tyranny but as a necessity for maintaining freedom over tyranny.
Six weeks before Kennedy gave this speech, Russian cosmonaut Yuri Gagarin had become the first man to orbit the Earth. Kennedy was clearly disturbed by the propaganda impact this had for Soviet communism.
"(I)f we are to win the battle that is now going on around the world between freedom and tyranny, the dramatic achievements in space which occurred in recent weeks should have made clear to us all, as did the Sputnik in 1957, the impact of this adventure on the minds of men everywhere, who are attempting to make a determination of which road they should take," he told Congress.
Kennedy was also concerned about whether freedom or tyranny would dominate realms beyond the Earth.
"Space is open to us now; and our eagerness to share its meaning is not governed by the efforts of others," said Kennedy. "We go into space because whatever mankind must undertake, free men must fully share."
Having framed the challenge this way, Kennedy said, "I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the earth."
The historian 2,000 years from now will see, as we can see now, that the America of the 1960s did send men to the moon and back.
The historian will see that the Soviet Union collapsed two decades later.
But then what will he see?