By Telegraph Sport
The 24-year-old produced a stunning display in gruelling weather conditions at Hayward Field, Eugene, Oregon to score 9,039 points, 13 more than Roman Sebrle's 11-year-old world record.
That left him an amazing 656 clear of second-placed Trey Hardee, the defending world champion, and former University of Oregan athlete. Eaton told USATF. org: "It is a representation of all the work I have put in.
"I love this field and it's special for it to happen here. It is a very special race.
"I felt in the moment ... I knew there was maybe not another opportunity to make this count. At 600 meters I knew there was no way I wasn't going to get the record."
But there was disappointment for Beijing gold medallist Bryan Clay, who fell during the hurdles and eventually finished 12th after also struggling in the discus.
He said: "It was a rough day for me, but it was fun to be a part of what Ashton had going on.
"It's unbelievable. I don't know if anyone has matured in the event as quickly as he did. It's mind-boggling."
Allyson Felix looked to have missed out on a place in the women's 100 metres team by the narrowest possible margin.
Felix dead-heated with Jeneba Tarmoh for third place in the shortest sprint, with an announcement to the crowd at Hayward Field, Eugene, stating that Tarmoh had been given the verdict by 0.0001 seconds.
The results were immediately reviewed, with USA Track and Field officials trying to determine a method of breaking the tie and awarding the third individual place in the squad for the London Games.
Carmelita Jeter won the race, with Tianna Madison finishing second to also secure her place.
Should Felix miss out, she will at least have the consolation of running in the 4x100m relay.
She said: "I am happy for my team-mate getting third, but I am really disappointed. Fourth is the worst."
But she added: "God has the bigger plan; you may think you have it but in the end things work out a certain way for a reason. Now I can focus fully on relays."
Jeter said: "I am in a very special place right now. I am trying not to get emotional. This is my first Olympic team! I am extremely blessed.
"I am excited to represent the U.S. in going to London. We have to represent the red, white and blue and I am sure that we will do that."
Dawn Harper will defend her 100m hurdles title after finishing first ahead of Kellie Wells and Lolo Jones, who will both accompany her to London.
Tyson Gay clocked 10 seconds flat in his first heat in the 100m, while Justin Gatlin continued his return from a doping ban with a time of 9.90 sec.