Thousands of spectators gathered on Tuesday to mark the 150th anniversary of President Abraham Lincoln's Gettysburg Address, considered one of the greatest speeches in American history for saying so much in so few words.
Lincoln delivered the 272-word speech in 1863 only months after the Battle of Gettysburg.
The battle is considered a turning point in the U.S. Civil War, but the future of the United States as one nation was by no means secured when Lincoln made his call for the nation to dedicate itself to democracy and liberty, said historian James McPherson, a keynote speaker at the commemorative event.
"Without Lincoln's leadership to make that victory possible, there might be today in North America, two or several United States," McPherson said.
"What kind of world would have emerged from two world wars in the 20th century without the existence of a strong United States? The answer is anybody's guess, but we can be assured it would not be the world we live in," he said.
Pennsylvania Governor Tom Corbett said Lincoln's words helped the deeply divided nation to heal.
"Lincoln wrote his words on paper, but he also inscribed them in our hearts," he said.
To help mark the historic event, U.S. Supreme Court Justice Antonin Scalia swore in 16 new U.S. citizens.
The son of Italian immigrants, he said growing up in America, he knew he could become whoever he wished to be.
In an aside, he noted that his grandmother "expected me to become president."
Some 3,500 Union soldiers are buried at Gettysburg.