All coverage
US marks 20th anniversary of 9/11: Live updates
By Melissa Macaya, Adrienne Vogt & Fernando Alfonso III
Biden, former presidents honor heroes, lives lost as nation marks 20th anniversary of 9/11
By Rhea Mogul & minyvonne burke
Biden visits all three attack sites on 20th anniversary of 9/11
By Jeff Mason & Trevor Hunnicutt
Biden marks 9/11 with visits to all three attack sites
By Shannon Pettypiece