Both New York and Washington stopped to mark the seventh anniversary of the September 11 attacks.
Ground Zero on the seventh anniversary of the attacks
In New York, the names of those who died at the World Trade Centre site were read out by relatives and students.
The ceremony in downtown Manhattan went silent four times, twice to mark the time when each plane hit the Twin Towers, and twice at the time when each tower fell.
The city's mayor Michael Bloomberg said the day would "live for ever in our hearts and our history".
He said the anniversary was about "New Yorkers, Americans and global citizens remembering the innocent people from 95 nations and territories that lost their lives that day."
Later today, the US presidential candidates, Senators Barack Obama and John McCain, will attend Ground Zero, after they agreed to suspend their campaigns for the White House for 24 hours.
In Washington, President George Bush said history would look back at America's response to the attacks and that "we did not tire, we did not falter and we did not fail".
"Since 9/11, our troops have taken the fight to the terrorists abroad so we do not have to face them here at home," he said.
The president also dedicated a memorial to the 184 people who died at the Pentagon.
A total of 2,974 people were killed on September 11, 2001, when terrorists hijacked four aircraft.
Two hit the World Trade Centre towers, one crashed near the Pentagon and the other came down near Pittsburgh.
last night i went to a junior high school because they band teacher happens to be my big sister's guy and the band did a little presentation in remembrance of 9/11. it was very moving. the woman sitting behind me was really sweet...she passed tissue my way. anywho, yesterday was september 11th. i was thinking about the many things going on in the country and how for one day, being yesterday, things seemed to calm just a bit. so many things went through my head yesterday. for one, i was thinking about all the lives that were lost during those number of hours. all the families that lost loved ones and for what reason? my heart was truly grieved by the thought that we live in such a world... where killing seems to be the popular thing to do... how terrible. i was thinking about what individuals who lost loved ones were thinking. strange as it may sound, i really was. i mean, thoughts of calls and watching the news and getting the terrible news may have been on repeat in the minds throughout yesterday. i was wondering if lots of people have already forgotten. i am not saying harp on it or anything like that but with political views aside and whatever else, i am glad to be a citizen of this country and well, the event of september 11th was something that rattled us. there were and are many things we should learn and should have learned as a result. like togetherness, unity, the pursuit of peace, so on. i also thought about terrorism. bear with me and don't leave mean notes if you disagree, that is unnecessary. we are all free to our own opinions. anywho, i was thinking about terrorism and how so many people label an entire group of people from a certain region of the earth terrorists because of something a group of radicals did. the people connected to this event were evil to the core. to do something so terrible they must have been. yes, that can be argued as well but that is my stand. after studying the doings of hitler for so many years, i think i have a pretty decent grasp on the meaning of evil and i will stand by my saying that the men responsible for the attack were pretty rotten. but that does not make the region they were from responsible for their actions. right? not everyone was aware that such a thing would happen. we have to be careful with where we place our judgements. i think we have to be concerned about caring for people, for each other. how are we going to make things better if we don't? anyway, i was just thinking... thoughts of peace.
