Cathleen Stone Island Outward Bound's Annual 4K Trail Run is the most unique and fun race in Boston! The 4K takes place on Cathleen Stone Island in the Boston Harbor, and in 2025 will be held on the afternoons of Wednesday, May 21st and Thursday, May 22nd. This event offers companies a fantastic opportunity to enjoy a team-building activity with their employees, and individual runners to experience a trail run like no other, in one of the most beautiful spots in Boston. Your participation in the 4K Trail Run directly supports Cathleen Stone Island Outward Bound's core mission to provide free, hands-on science learning and social emotional development to Boston students.