By Darlene Superville Associated Press President Joe Biden speaks during an event to mark Amtrak’s 50th anniversary at 30th Street Station in Philadelphia on Friday. Patrick Semansky | AP photo �� Listen to this ‘I wouldn’t have missed this for the world,’ President Joe Biden said Friday of an event to mark Amtrak’s 50th anniversary. Patrick Semansky | AP photo President Joe Biden arrives with his granddaughters Finnegan Biden, right, and Maisy Biden, during an event to mark Amtrak’s 50th anniversary at 30th Street Station in Philadelphia. Patrick Semansky | AP photo PHILADELPHIA — President Joe Biden, once a regular Amtrak rider, helped the nation’s passenger rail system celebrate 50 years of service Friday.