Over the weekend, participants can walk up to 39 miles along Lake Michigan.
Sunday’s trek will include the final 13-miles of the route.
Walkers raised more than $6 million towards research to find a cure for breast cancer.
Since 2012, the weekend-long event has raised more than $55 million dollars for organizations and institutions in Illinois and across the Midwest.
The marathon will conclude Sunday in a closing ceremony at Soldier Field.