He amassed a 37-7-1 record with 26 KOs, and along the way held the U.S. Boxing Association's middleweight (1989) and super-middleweight (1995) titles. He was inducted into the New Jersey Boxing Hall of Fame in 2001.
He retired from the ring shortly after losing a 168-pound title bout in 1995 against Roy Jones Jr., then widely considered pound-for-pound the best boxer in the world.
James Toney, a heavyweight champion who also held the title in two other divisions, recalled his 1993 bout with Thornton earlier this week in a blog posting on the Ring Web site.
"I thought I was gonna knock him out easy. He was squared up with his chin right there for me to hit but I hit him with every punch I had and he wouldn't budge," Toney wrote. "I hit him with my best left hook and he didn't blink."
After hanging up his gloves, Mr. Thornton continued working for the postal service, delivering mail in Bellmawr six days a week, said his friend, Bellmawr postmaster Frank Murphy. Customers on his route often asked for his autograph.
After 15 years as a carrier, he served an additional 10 years as a customer-service supervisor.
"I was his postmaster for four years," Murphy said. "I've never met anyone with such dedication and determination."
Just before Mr. Thornton was to face Toney, a reporter asked him whether he would ever quit his job as a letter carrier, Murphy said.
Mr. Thornton, Murphy said, responded: "Just because I might win a championship doesn't mean I won't work at the post office."
Though he got a kick out of being called the Punching Postman, the soft-spoken letter carrier rarely spoke of his former life as a fighter, Murphy said.
"I'd have to drag it out of him," Murphy said. "That was in his past, here was where he was now."
He began boxing at 19 while attending West Chester University, becoming the 156-pound national collegiate boxing champion in 1979-80. He turned pro in 1983 and won his first bout in less than 20 seconds.
He earned his nickname in 1985.
"There were other names, like 'TKO Tony' and 'Thunder Thornton,' " he told an Inquirer reporter in 1993, "but the 'Punching Postman' stuck."
On Aug. 30, Mr. Thornton rode his motorcycle from Philadelphia across the Ben Franklin Bridge. He was taking the turnoff onto I-676 when he was clipped by a bus and tossed against a wall, Murphy said.
Mr. Thornton is survived by his girlfriend, Kim Eikerenkoetter; and his children, Ashley and Tony Jr.
Funeral arrangements had not yet been set.
Contact staff writer Sam Wood at 215-854-2796 or firstname.lastname@example.org.