On a sweltering July day in 1968, 1,000 young athletes gathered at Soldier Field in Chicago, where they ran, jumped, threw balls and swam.

Few spectators were there to witness the inaugural Special Olympics International Summer Games. But the competitors, all boys and girls with intellectual disabilities, helped usher in a new and more inclusive era in sports, at a time when children with special needs were often locked away at home or shipped off to institutions.