Its about an hour and a half commute from Wilmington, DE, to Washington, D.C. (even less with the Acela).
From Biography.com: "In November 1972 , in a tight race with a large turnout, Biden won an upset victory to become the fifth-youngest U.S. senator elected in the nation's history...A week before Christmas in 1972, Biden's wife and three children were involved in a terrible car accident while out shopping for a Christmas tree. The accident killed his wife and daughter, and severely injured both of his sons, Beau and Hunter...At the encouragement of his family, Biden decided to honor his commitment to represent the people of Delaware in the Senate. He skipped the swearing-in ceremony for new senators in Washington and instead took the oath of office from his sons' hospital room. In order to spend as much time as possible with his sons, Biden decided to continue to live in Wilmington, commuting to and from Washington each day by Amtrak train, a practice he maintained through his entire long tenure in the Senate."
Jim