At about 12:40 a.m., the man was found dead with stab wounds to the head and neck in the 8500-block of South Peoria, police said.
Family identified the man was Robert Cox, of the city's Humboldt Park neighborhood.
Community activist Andrew Holmes said Cox was an Army veteran.
A $1,000 reward was being offered. Anyone with information is asked to call 800-883-5587.