Hanson's body was found in a cornfield near 87th Street and Modaff Road almost 50 years ago, on July 8, 1972.
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Investigators said she had been sexually assaulted and stabbed 36 times. She was last seen leaving her home on a bike, police said.
"She was very personable, a very sweet girl," said Peggy Thompson, Hanson's neighbor. "She was only a couple of years older than us, but she babysat some of the kids in the neighborhood."
Barry Lee Whelpley, 76, of Mounds View, Minn., was arrested Wednesday and charged with first-degree murder in connection with the crime, according to Naperville Police Chief Robert Marshall and Will County State's Attorney James Glasgow. He appeared in court Friday following extradition. Whelpley's bond was set at $10 million.
Police said DNA was the key to identifying Whelpley as a suspect. As a 27-year-old he lived about a mile from Hanson. One of his relatives apparently used a commercial DNA service to explore family history, which helped Dr. Colleen Fitzpatrick link him to a small sample of DNA from the crime scene. Naperville police took it from there.
"Our department never in five decades gave up looking for Julie's killer," Marshall said.
WATCH: Naperville police discuss Hanson case
Marshall said Hanson had borrowed her brother's bike to go to a baseball game that July day, but she never made it. She was reported missing, and her bike was later found on a gravel road near Knoch Knolls Road and 87th. Then officers found her body.
"No one locked doors. We knew everybody, and then this happened, and I've called it the end of the age of innocence," Thompson said. "Because it immediately changed to a very fearful existence, especially for us as kids."
"This horrific crime has haunted this family, this community and this department for 49 years," Marshall said. "The investigation and resulting charges were truly a team effort that spanned decades, and I could not be more proud of the determination and resourcefulness of our investigators, both past and present, who never gave up on Julie."
Hanson's parents are no longer alive, but her brother and sister were at the news conference and expressed their gratitude in a written statement.
"I'm personally am very thankful that they got someone. I'm just disappointed that he lived free for 50 years," Thompson said.
Last year, Naperville officials announced that they had checked the DNA from Bruce Lindahl, who died while fatally stabbing another in Naperville in 1981, but that he was not a positive match for the Hanson case.
Lindahl's murder of Pamela Maurer of Woodridge in 1976 was similar to that of Hanson, so officials wanted to compare just in case, as authorities said Lindahl had multiple victims.
Anyone with additional information regarding the investigation is encouraged to contact the Naperville Police Department at (630) 420-6665 and ask for the Investigations Division.
This is a developing story; check back with ABC 7 Chicago for updates.