evidence: President Joe Biden speaks to members of the media as he visits the Shanksville Volunteer Fire Department in Shanksville, Pennsylvania, on September 11. [...] President Biden participated in a wreath-laying ceremony at the United 93 memorial in Shanksville, Pennsylvania, to mark the 20th anniversary of the Sept. 11, 2001, attacks. [...] President Biden and first lady Jill Biden will travel to all three sites of the 9/11 terrorist attacks today, marking the 20th anniversary of the deadly day, according to the White House.