After Amtrak started, they ran the Broadway and National connecting train with electric (GG-1) power from Washington to Baltimore to Harrisburg via the recent freight-only Columbia and Port Deposit ("Port Road") via Safe Harbor. At Harrisburg they were combined with the New York sections. As mentioned earlier, when the Broadway started going into 30th Street Philadelphia to change power (previously it only served North Philadelphia when it used the 'subway' bypass at Zoo; there was direct service from Philly, but alas no more service thru to Baltimore except by connection at Philly. The reborn Capitol gave Washington service direct to Pittsburgh on the B&O route.
All true except that for a brief period the 441 and 41 hooked up at Philadelphia after the Broadway started to run through Philadelphia 30th St. See:
http://www.timetables.org/full.php?group=19800803&item=0036 . Until this ended in October 1981 when the connection point moved to Pittsburgh, there still was direct one seat ride from Baltimore to Harrisburg.
Incidentally, also for the duration of time when the 41 - 441 connection was at Harrisburg, there was a period when the Washington section ran through Philadelphia 30th St. Station and not via the Port Road. See for example:
http://www.timetables.org/full.php?group=19800203&item=0036 . So 30th Street got direct service to Chicago via 441, before 41 started going through 30th St.