Among those attending the weeklong trial was Ridulph's playmate, Kathy Chapman, who testified that McCullough was the young man who approached the girls as they played, asking if they liked dolls and if they wanted piggyback rides.
"A weight has been lifted off my shoulders," Chapman said with a smile on the courthouse steps after the conviction was announced. "Maria finally has the justice she deserves"
Others in court included Jeanne Taylor, 57, who said children in the close-knit town lived in terror after Ridulph's disappearance.
It all happened in an era when grease-backed hair and automobile tail fins were still in, and when child abductions, if not unheard of, rarely made headlines.
This one did.
President Dwight Eisenhower and FBI director J. Edgar Hoover asked to be kept apprised of the search for the girl, which lasted five months and ended when her decomposed body was found in a forest 120 miles from her hometown.
Testimony, which lasted four days, was often dramatic and, for friends and family, deeply emotional.
The victim's brother, Charles Ridulph, took to the stand to describe his sister as a sweet, smart, pretty and outgoing child beloved by the family.
McCullough's half-sister told the court that their mother, Eileen Tessier, said on her death bed in 1994 that McCullough whose name was then John Tessier had killed Ridulph.
"She grabbed my wrist and said, 'Those two little girls, the one that disappeared, John did it,'" Janet Tessier said.
After the verdict, Janet Tessier's eyes were red with tears.
"He is as evil as prosecutors painted and some," she said.
The star witness was Chapman, the friend who had been playing with Ridulph on Dec. 3, 1957, on the corner of Archie Place and Center Cross Street.
She said a young man calling himself "Johnny" approached, asking if they liked dolls and offering piggyback rides. After Ridulph ran home to get her doll, Chapman went to grab mittens. When she returned, her friend and the man were gone.
She never saw her friend alive again.
A prosecutor laid out black-and-white photographs of similar looking men from the era on the stand for Chapman, and she pointed to one of McCullough saying she was sure he was the man who called himself "Johnny."
A Seattle investigator who interviewed McCullough last year, Irene Lau, said McCullough remembered Maria, calling her "stunningly beautiful." But he maintained he had nothing to do with her disappearance or death.
McCullough was on an early list of suspects in 1957. But he had an alibi, saying that on the day, he had traveled to Chicago to get a medical exam before enlisting in the Air Force.
The case was reopened after his old girlfriend contacted police with evidence calling his alibi into question she had found his unused train ticket from Rockford to Chicago on the day Ridulph disappeared. He was arrested on July 1, 2011, in Washington state at a retirement home where he worked as a security guard.
The trial has been complicated by faded memories and, in McCullough's case, an absence of physical evidence.
McCullough waived his right for a jury trial and opted for a bench trial instead.
Among the other state witnesses were inmates jailed with McCullough as he awaited trial.
One said he overheard McCullough say he strangled Ridulph with a wire. Another said McCullough told him he killed her accidentally that she fell as he gave her a piggyback ride, then smothered her as he tried to stop her from screaming.
Prosecutors say McCullough stabbed the girl in the throat and chest.
In his opening statement, DeKalb County State's Attorney Clay Campbell described the night Maria went out to play on a street corner with her friend.
"This ordinary night would end in horror," he said. "It would end with this defendant dumping her body in the cold, dark woods like a piece of garbage."