Authorities said security at the 10-mile race kicking off from Montrose Harbor had been increased by 20 percent.
Police were asking everyone to be as vigilant as possible for anything suspicious. Family members and friends on the sidelines also were asked to remain aware and alert.
Approximately 1,800 people took part in Saturday's run, one of the first since Monday's Boston Marathon attacks. Many participants told ABC7 Chicago they did not hesitate to register for the race.
"Everyone is going to laugh across the finish line," said runner Harold Rodgers. "They are taking off. It is a cool thing they did, and people here are not worried."
The executive director of the race said she saw a small spike in the number of runners registering for the race after Monday's bombings in Boston.