The classic race of the Olympics began on the plains of Marathon and finished in the stadium that hosted the first of the modern Games.
Noguchi broke away from the pack about two-thirds of the way through the race and held on to win in the time of 2:26.20.
Catherine Ndereba of Kenya won the silver medal, finishing 12 seconds behind.
Kastor was as far back as 18th place late in the race, but steadily passed runners until she moved into third. She took the bronze, exactly a minute behind the winner.
As she entered the stadium and began her final lap, Kastor's face broke with emotion and tears began to run down her face.
"I was bawling the entire last lap," she said.
Kastor is the first American to even finish among the top eight of the women's marathon since Joan Benoit won the event the first time it was contested in 1984.