The boy faces charges of aggravated criminal assault and manufacturing and disseminating child pornography. He was not named because of his age.
The girl was allegedly assaulted by five or six males last month.
Around 40 people were said to have been watching the stream at one point but nobody reported the incident to police.
A teenager had alerted a relative of the girl's, Reginald King, to the assault.
"There were adults who saw this. None of them had the wherewithal to say, 'Hey, I gotta call someone'," Mr King said.
The girl had been dropped off near her home after attending church with her family on 19 March. She then disappeared and was found on 21 March after the alleged assault was filmed.
She was reunited with her mother but the family has had to be relocated as it suffered threats and taunts. Police expect to make further arrests.
A spokeswoman for Facebook said: "Crimes like this are hideous and we do not allow that kind of content.
"We take our responsibility to keep people safe on Facebook very seriously and will remove videos that depict sexual assault and are shared to glorify violence."
In January, Chicago police arrested four people following a separate incident in which a man's alleged assault was live streamed, also on Facebook Live.