Reds players and officials visited the residence of US president Barack Obama for a photo opportunity and private tour of Washington DC's famous landmark.
"It was fantastic, we all enjoyed it," Sir Alex said afterwards. "It was fascinating. I'd been before but it still excites. It's such a historic and incredible place."
The American capital is the fifth and final destination of United's pre-season tour and the Reds are preparing for a rematch with Champions League final foes Barcelona at FedExField on Saturday.
Click the image above to see a gallery of pics of United leaving New Jersey, arriving in Washington and visiting the White House.