Apart from re-electing their first black president, Americans this year have also been observing the 150th anniversary of the Civil War, which led to the abolition of black slavery.
The two are deeply connected milestones in the journey of the world's most powerful nation.
Barack Obama might now be remembered for the change he wrought, not just for who he was. But the Civil War is never really forgotten. It helped to shape everything that America has become.
Australians can find this perplexing, because we have had no Civil War of our own, and I trust we never will.
Killing each other is a difficult concept to get your head around, especially on this scale. More Americans - some 600,000 - died in the Civil War than in both world wars combined.
I have spent months tramping around the old battlefields because this conflict above all others contained so many contradictions and madnesses.
Robert E. Lee, for example, was offered command of both armies. He turned the north down and opted to lead the south because he considered himself a Virginian first and an American second.
That was the point of the whole war, really. It is remembered as the war which freed the slaves, and so it was. But it was fought in equal or greater measure to decide whether the union - the USA we know today - could and should survive. As war-time president Abraham Lincoln famously said: "A house divided against itself cannot stand."
General Lee lived just across the Potomac River from Washington, DC. The north ended up burying its dead at his very doorstep, a symbolic move which led to the creation of Arlington national cemetery, where the body of John F. Kennedy lies.
Ulysses S. Grant, the general who finally won the war for the north and later became president, owned a slave himself.
The war divided states, cities and even families, pitting brother against brother.
When it started with shots fired at Fort Sumter, South Carolina, it was expected to last just a few days or weeks.
The opposing capitals, Washington and Richmond, were barely 150 kilometres apart, not that much further than Sydney and Wollongong.
Visit the southern states today and you will see confederate flags flying in many a front yard.
The south hasn't forgotten the war, but there's a strong element of denial in the way it's remembered.
Some southerners still call it The War Of Northern Aggression.
Lincoln never uttered a sentence so mistaken as when he said after the Battle of Gettysburg: "The world will little note nor long remember what we say here."
His Gettysburg address remains a source of inspiration for those who pray that "government of the people, by the people, for the people shall not perish from the earth".
Everyone on earth has an interest in America's ability to wield its power wisely, none more than a military ally like Australia.
Many remain disturbed by the use of America's military might in modern times, though Obama has extricated the US from one unnecessary war in Iraq and is winding things down in Afghanistan.
I fervently hope Obama, his successors and all of their enemies are forever touched by what Lincoln fetchingly called "the better angels of our nature".