Besides being flat and fast, the course provides a bit of Olympic symmetry since it will be used for the 2016 Games if Chicago wins its bid to host. Kastor, the American record holder, broke her foot at the Beijing Olympics.
"I have high expectations for the race," said Kastor, who won it in 2005. "I'm really excited to get after it and lower my personal record."
Kastor set the U.S. record of 2 hours, 19 minutes and 36 seconds at the 2006 London Marathon and believes she can better that mark, and even get below 2:18. Paula Radcliffe of Britain holds the women's world record, running a 2:15:25 at London in 2003.
The 36-year-old Kastor is the first elite woman to commit to run in Chicago on Oct. 11.