Weaver died of complications from cancer Friday at his home in Ridgway, in southwestern Colorado, his publicist Julian Myers said.
Weaver was a struggling actor in Hollywood in 1955, earning $60 a week delivering flowers when he was offered $300 a week for a role in a new CBS television series, "Gunsmoke." By the end of his nine years with "Gunsmoke," he was earning $9,000 a week.
When Weaver first auditioned for the series, he found the character of Chester "inane." He wrote in his 2001 autobiography, "All the World's a Stage," that he said to himself: "With all my Actors Studio training, I'll correct this character by using my own experiences and drawing from myself."
The result was a well-rounded character that appealed to audiences, especially with his drawling, "Mis-ter Dil-lon."
At the end of seven hit seasons, Weaver sought other horizons. He announced his departure, but the failures of pilots for his own series caused him to return to "Gunsmoke" on a limited basis for two more years. The role brought him an Emmy in the 1958-59 season.
In 1966, Weaver starred with a 600-pound black bear in "Gentle Ben," about a family that adopts a bear as a pet. The series was well-received, but after two seasons, CBS decided it needed more adult entertainment and cancelled it.
Next came the character Sam McCloud, which Weaver called "the most satisfying role of my career."
The "McCloud" series, 1970-1977, juxtaposed a no-nonsense lawman from Taos, N.M., onto the crime-ridden streets of New York City. His wild-west tactics, such as riding his horse through Manhattan traffic, drove local policemen crazy, but he always solved the case.
He appeared in several movies, including "Touch of Evil," "Ten Wanted Men," "Gentle Giant," "Seven Angry Men," "Dragnet," "Way ... Way Out" and "The Bridges at Toko-Ri."
Weaver also was an activist for protecting the environment and combating world hunger.
He served as president of Love Is Feeding Everyone (LIFE), which fed 150,000 needy people a week in Los Angeles County. He founded the Institute of Ecolonomics, which sought solutions to economic and environmental problems. He spoke at the United Nations and Congress, as well as to college students and school children about fighting pollution and starvation.
"Earthship" was the most visible of Weaver's crusades. He and his wife Gerry built a solar-powered Colorado home out of recycled tires and cans. The thick walls helped keep the inside temperature even year around.
"When the garbage man comes," Jay Leno once quipped, "how does he know where the garbage begins and the house ends?"
Weaver responded: "If we get into the mindset of saving rather than wasting and utilizing other materials, we can save the Earth."
The tall, slender actor came by his Midwestern twang naturally. He was born June 4, 1924, in Joplin, Mo., where he excelled in high school drama and athletics. After Navy service in World War II, he enrolled at the University of Oklahoma and qualified for the Olympic decathlon.
He studied at the Actors Studio in New York and appeared in "A Streetcar Named Desire" opposite Shelley Winters and toured in "Come Back, Little Sheba" with Shirley Booth.
Universal Studio signed Weaver to a contract in 1952 but found little work for him. He freelanced in features and television until he landed "Gunsmoke."
Weaver appeared in dozens of TV movies, the most notable being the 1971 "Duel." It was a bravura performance for both fledgling director Steven Spielberg and Weaver, who played a driver menaced by a large truck that followed him down a mountain road. The film was released in theaters in 1983, after Spielberg had become director of huge moneymakers.
Weaver's other TV series include "Kentucky Jones," "Emerald Point N.A.S.," "Stone" and "Buck James." From 1973 to 1975, he served as president of the Screen Actors Guild.
Weaver is survived by his wife; sons Rick, Robby and Rusty; and three grandchildren.