Sha'Carri Richardson challenger Shericka Jackson drops from 100m

(Photo credit: Kirby Lee-USA TODAY Sports)

PARIS -- American world champion Sha'Carri Richardson, who holds the world's top time of 10.71 seconds in the 100 meters this year, will start as the favorite for the gold medal with two-time Jamaican 200-meter world champion Shericka Jackson withdrawing from the race in Paris.

The United States'last 100-meter title was 28 years ago, when Gail Devers topped the podium at the 199