Dante Rivers died Friday at Comer Children's Hospital, the Cook County Medical Examiner's Office said.
Griffith police said emergency crews responded to the 1200-block of North Wood Street on July 22, after the boy was found in a backyard swimming pool.
He had wandered out of a home in the area, causing his parents and neighbors to go looking for him, police said.
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Emergency responders performed life-saving measures on the unconscious boy, who was taken to the hospital for treatment.
"The community mourns with the family for their tragic loss," Griffith police said in a statement.