Davenport Police say human remains found near DeWitt earlier this month are those of Breasia Terrell.
The then 10-year-old went missing from Davenport late July 9 or early July 10, launching a massive search effort that spanned several counties.
Authorities announced the development at a press conference Wednesday.
"This is heartbreaking," said Chief Paul Sikorski, breaking down in tears.
Fishermen made the discovery March 22 in a pond in a rural area.
The investigation has included four investigators from Davenport and two FBI agents, who followed-up on 170 tips, conducted hundreds of interviews and served "over 60" search warrants related to Breasia's disappearance, authorities said in December.
Criminal charges have not been filed, and police declined to take questions about what has now become a homicide investigation.
This story will be updated.