Fort Monroe "was the site of the first slave ships to land in the New World," Obama said during the Oval Office signing.
"But then in the Civil War, almost 250 years later, Fort Monroe also became a refuge for slaves that were escaping from the South, and helped to create the environment in which Abraham Lincoln was able to sign that document up there -- the Emancipation Proclamation."
Obama said the National Monument designation would bring millions of dollars to the region and create 3,000 jobs.
"There's a strong economic component to this. We think we're going to see additional jobs in Virginia as a consequence of this. But for those members of Congress who are here, I still need some action from Congress on the American Jobs Act and other steps," the president said.
Obama also remarked on the passing of Dorothy Rodham, Secretary of State Hillary Clinton's mother.
"Ms. Rodham was a remarkable person. … For her to have been able to live the life that she did and to see her daughter succeed at the pinnacle of public service in this country, I'm sure was deeply satisfying to her. … I know that she will be remembered as somebody who helped make a difference in this country and this world," he said.