His death after a long illness was confirmed by his son, Stuart.
The red-haired, freckle-faced Milner had more than a dozen years of work in films and television behind him in 1960 when he began plying the highways and byways of America on "Route 66," portraying Yale dropout Tod Stiles opposite George Maharis' streetwise New Yorker Buz Murdock.
The hourlong dramatic series on CBS, in which the two young men became involved in the problems of the people they met as they crisscrossed the country and worked a variety of jobs, was shot on location.
"We didn't pretend to be on 66 either," Milner told the Chicago Tribune in 1992. "We always said where we were. If we were in Vermont or in Texas, the audience knew it."
Weather dictated where they'd film the show.
"We'd start late in the summer in the north, say in Cleveland, or in New England," recalled Milner. "Then we'd go south as the winter came, so we'd be warmer."
The series was called "Route 66," Milner said, because that highway had become symbolic of American wandering and of the "search for a new life."
A director on the series once described Milner as having a "sunny personality," as opposed to Maharis' "glowering sex appeal."
Sex appeal clearly gave the dark-haired Maharis the edge over Milner in terms of youthful fan appeal: On a good month, according to a 1963 TV Guide story, Maharis' fan mail reached 5,000 letters, compared to Milner's average of about 1,800.
Sterling Silliphant, the series' co-creator who wrote the majority of the scripts, told the magazine that "the teenagers are crazy about [Maharis], but he bores their parents stiff. He's too primitive. The adults like Marty because he's a gentleman. They only tolerate George because Marty seems to like him."
Milner, whose wife and children often traveled with him on location, reportedly had an evolving off-camera relationship with his Corvette sidekick.
"Maharis and I got along fine — until I found out he didn't like me," Milner told TV Guide after Maharis exited the series after a bout with infectious hepatitis and an ensuing battle with the show's producers, whom he complained overworked him so much after he returned to the show that he had a relapse.
Glenn Corbett took over as Milner's new traveling companion — as returning Vietnam War veteran Linc Case — in 1963 and remained with the show until it ended in 1964.
Over the next few years, Milner did TV series guest shots, appeared in a few movies, including "Ski Fever" and "Valley of the Dolls," and appeared on Broadway with Dyan Cannon in "The Ninety Day Mistress," which had a brief run in 1967.
He returned to series television in 1968 as Officer Pete Malloy in "Adam-12," the
The series, which focused on the daily routine of two uniformed LAPD officers assigned to patrol-car duty, ran until 1975.
"People said, 'It looks like you guys like each other.' We got this repeatedly," McCord told The Times Monday. "And we did. We never had to pretend."
Milner and McCord were reunited in the police drama "Nashville Beat," a TV movie that aired on cable's TNN in 1989.
Although fans continued to recognize Milner long after "Route 66" and "Adam-12" ended, he downplayed his TV-star status.
"I was never a celebrity," he told People magazine in 1995, "just a working actor."
Milner was born in Detroit on Dec. 28, 1931. His mother was a dancer with the Paramount theater circuit and his father was a construction worker who later went into movie distribution.
As a child, Milner moved with his family to Seattle, where he began acting in a theater group, and then moved to Los Angeles as a teenager.
He made his movie debut playing one of the sons in the comedy "Life with Father," the 1947 movie starring William Powell and Irene Dunne.
Shortly after filming ended, Milner was stricken with polio from which he recovered within a year.
A graduate of North Hollywood High School, he took classes at San Fernando Valley State College and then spent a year at USC before dropping out to focus on his acting career.
"I was never a child star," Milner told the Los Angeles Times in 1992. "I was just somebody who got two or three jobs before I was a young adult."
That included a small role as a private in the 1949 war movie "Sands of Iwo Jima," starring John Wayne.
It was while he was playing a part in the 1950 war film "Halls of Montezuma" that he met an actor who would play a major role in his career: Webb.
During filming, Milner won $150 from Webb in a gin rummy game. Webb didn't pay up at the time. But a couple of months later, he phoned Milner and told him to pick up his check at NBC Radio, where Webb was doing his series "Dragnet."
When Milner came for his check, Webb mentioned that he had a lot of parts on the show that Milner could play.
"So I went to work in the 'Dragnet' radio series," Milner recalled in a 1973 TV Guide interview. "Because I couldn't be seen, I played old guys and middle-aged guys. One whole summer I was even Jack's police-partner in the series."
Milner's work on both the radio and TV versions of "Dragnet" continued after he was drafted into the Army in 1952 and stationed at Ft. Ord near Monterey, where he directed military training films and served as emcee for a Ft. Ord-based touring show.
"Whenever I could get a three-day pass and get home, even if [Webb] didn't have a part for me, he would write one so I could make $75," Milner said in the 1992 Times interview.
After his discharge, he appeared in movies such as "Francis in the Navy," Webb's "Pete Kelly's Blues," "Sweet Smell of Success" and "Marjorie Morning Star."
He also had stints as a regular on the 1950s situation comedies "The Stu Erwin Show" and "The Life of Riley," as well as TV guest appearances on series such as "Navy Log," "Playhouse 90" and "The Twilight Zone."
When "Adam-12" ended after seven years, Milner starred as Karl Robinson in the 1975-76 ABC adventure series "Swiss Family Robinson."
In addition to occasional stage work, he made TV guest appearances on shows such as "Fantasy Island," "MacGyver" and "Murder, She Wrote" — as well as a stint playing a socialist bookshop owner on "Life Goes On" in 1992.
An avid fisherman, he co-hosted the popular weekend call-in radio talk show "Let's Talk Hook-Up" from 1993 to 2004.
Besides his son Stuart, Milner is survived by his wife, Judy, whom he married in 1957; daughter Molly; son Andrew; and three grandchildren. Daughter Amy died in 2004.
For the record, 1:04 p.m., Sept. 7: An earlier version of this post said Milner died Monday at age 82. He died Sunday at 83.
McLellan is a former Times staff writer.