James Arness, who presided over the frontier town of Dodge City as television’s most enduring western hero, the laconic, fair-minded and incorruptible Marshal Matt Dillon of the two-decade-long series “Gunsmoke,” died June 3 at his home in Los Angeles at 88. The cause of death was not reported.

Mr. Arness, who was a rugged 6-foot-7, stood tall in the dusty streets of Dodge City, Kan., portraying a U.S. marshal whose badge represented more than just the force of law. He was the embodiment of quiet moral authority, a sensitive arbiter of conflict in a rough-and-ready cow town — “Gomorrah of the plains, they call it,” as he said in the show’s first episode. Only when pushed to the limit would Marshal Dillon pull his six-gun from its holster.

When “Gunsmoke” premiered in 1955, it was considered a new breed of “adult western,” with well-drawn characters and complex plots that, despite its name, took the show beyond outlaws and gunfights.

“What made us different from other westerns,” Mr. Arness told the Associated Press in 2002, “was the fact that ‘Gunsmoke’ wasn’t just action and a lot of shooting; they were character-study shows.”

Mr. Arness, who was recommended for the role of Matt Dillon by his friend John Wayne, was the center of an ensemble that included Milburn Stone as the gentle, scholarly Doc Adams; Amanda Blake as Kitty Russell — “Miss Kitty” — who ran the Long Branch saloon; and Dennis Weaver as Mr. Arness’s limping deputy sidekick, Chester Goode. After Weaver left the show in 1964, Ken Curtis joined the cast as the memorable comic character, Festus Haggen.

“Gunsmoke” aired on CBS for 20 years, but in Dodge City it was forever 1873. Other westerns came and went, but “Gunsmoke” ranked among the most popular programs year after year. When it was canceled in 1975, it was the last western on TV at the time.

No other scripted shows have run as long except “The Simpsons,” which reached its 20th year in 2009, and “Law & Order,” which left the air last year after 20 seasons. Neither show is within 150 episodes of “Gunsmoke’s” total of 635.

As the show evolved, the opening credits changed from a main-street shootout to a scene of Marshal Dillon galloping his horse across the prairie. His relationship with Miss Kitty developed to the point that they shared a kiss during one episode in 1973. They never married, though, and the social order of Dodge City remained intact.

“Matt Dillon is still the all-time, all-star marshal, pure, square-shouldered square-shooter, yet he never hogs the screen,” New York Daily News culture critic Gerald Nachman wrote in 1973, summing up the appeal of “Gunsmoke” and Mr. Arness’s archetypal central character. “Half the time you hardly know he’s in town, but he casts a tall shadow.”

James King Aurness — he dropped the “u” after arriving in Hollywood — was born May 23, 1923, in Minneapolis. His younger brother was actor Peter Graves, the star of the 1960s series “Mission Impossible” and the comic “Airplane!” films. Graves died last year at 83.

Mr. Arness left Beloit College in Wisconsin to join the Army during World War II. When his infantry unit came ashore at Anzio, Italy, in 1944, the lanky Mr. Arness was the first soldier off the landing craft, in order to gauge the depth of the water.

Later, during a patrol, he was severely wounded in the right leg and foot by machine-gun fire. He spent more than a year in military hospitals and was awarded the Bronze Star Medal and Purple Heart.

After working briefly as a radio announcer in Minnesota, Mr. Arness moved to Hollywood in 1946, took acting lessons and landed a part as Loretta Young’s brother in the 1947 movie “The Farmer’s Daughter.”

He appeared in the science fiction films “The Thing From Another World” (1951) — he played the Thing — and “Them!,” about man-eating mutant ants (1954). He signed on with Wayne’s production company and appeared with him in four movies, including “Hondo” (1953) and “The Sea Chase” (1955).

After “Gunsmoke” left the air, Mr. Arness starred in the TV movie and miniseries “How the West Was Won” and the 1981 TV detective drama “McClain’s Law.” He reprised the role of Marshal Dillon in several TV movies in the 1980s and 1990s.

“Gunsmoke” made Mr. Arness a millionaire many times over, and he owned several houses and a cattle ranch. He published an autobiography in 2001.

His first marriage, to actress Virginia Chapman, ended in divorce. A daughter from his first marriage, Jenny Aurness, committed suicide in 1975; Craig Aurness, a stepson from his first marriage, whom he adopted, died in 2004.

In 1978, Mr. Arness married Janet Surtees. Besides his wife, survivors include a son from his first marriage, Rolf Aurness, who was the world surfing champion in 1970; a stepson, Jim Surtees; and six grandchildren.

Mr. Arness was nominated three times for an Emmy Award but did not win. His acting style was stoic, with much of the feeling beneath the surface.

In one of the final Matt Dillon spinoffs, “Gunsmoke: The Long Ride” (1993), a brash young deputy asked, “How many bullet holes you got in you, Dillon?”

Fixing him with an icy, unflinching glare, Mr. Arness replied, “I’ve had my share.”