Final project of John Spencer, who quit acting in movies to fully concentrate in his role as Leo McGarry (which earned him one Emmy and two SAG Awards). He then passed away of a heart attack during the final season.
Martin Sheen was originally only scheduled to appear in four episodes per season. It was only after the pilot was filmed that it was decided to make him a regular cast member.
Once while the show was filming in Georgetown at about three o'clock in the morning, an irate lady reportedly came out in a bathrobe with a bunch of guys. She said, "What the hell's going on? I have an early morning at the State Department, and, by the way, you people don't even have a Secretary of State on your show, and I think you should have one, and it should be a woman." The woman was Madeleine Albright.
Leo's "Big Block of Cheese" story is true. Andrew Jackson received an enormous block of cheese from the people of New York City, and when he hadn't touched it in two years, gave it to the people of D.C. to celebrate Washington's birthday. They finished it in two hours.
Josiah Bartlett of New Hampshire was a member of the Second Continental Congress in 1776, and signed the Declaration of Independence. President Josiah Bartlet (Martin Sheen) is supposed to be his descendant, despite the different spelling of his last name.