His death was confirmed by his daughter, Hope Juber.

Mr. Schwartz weathered painfully dismissive reviews to see his shows prosper and live on for decades in syndication. Many critics suggested that they were successful because they ran counter to the tumultuous times in which they appeared: the era of the Vietnam War and sweeping social change.

Give or take a month or so, the original network run of “The Brady Bunch” coincided with two major upheavals in American society. The show, about a squeaky-clean blended family in California, began in 1969, shortly after Woodstock, and ended in 1974, soon after President Richard M. Nixon’s resignation following the Watergate scandal.

Mr. Schwartz’s work may have been seen as lighthearted entertainment, but some scholars of popular culture took it very seriously. David Marc and Robert J. Thompson, authors of “Prime Time, Prime Movers,” in which they advance an auteur theory of television, considered Mr. Schwartz an innovator who made a “surgical strike into the national psyche.”

Describing the advent of “Gilligan’s Island,” which told the story of seven very different castaways stranded on a desert island, they wrote, “Schwartz was pioneering a dramatic matrix built upon the emerging cultural concept of the ‘support group’: a collection of demographically diverse characters thrown together by circumstance and forced to become an ersatz ‘family’ in order to survive.”

Mr. Schwartz, in a 1996 interview, said that he had always planned the series as a social statement, the message being, “It’s one world, and we all have to learn to live with each other.”

Once or twice a year, he added, he received word of an academic paper whose author claimed to have uncovered the “real meaning” of the series, also stating that its creator probably had no idea what he was really saying.

Not so. Mr. Schwartz remembered describing the idea of “Gilligan’s Island” to William S. Paley, then chairman of CBS, as a microcosm. Mr. Paley, he recalled, blanched and said, “Oh, God, I thought it was a comedy show,” to which Mr. Schwartz quickly responded, “But it’s a funny microcosm!”

Mr. Schwartz was also largely responsible for his shows’ theme songs, which spelled out the premises in detail. “The Ballad of Gilligan’s Island,” which Mr. Schwartz wrote with George Wyle, told the story of those castaways and how they ended up on that island. It began:

Just sit right back and you’ll hear a tale,
A tale of a fateful trip
That started from this tropic port
Aboard this tiny ship.

The “Brady Bunch” theme, which Mr. Schwartz wrote by himself, told the story of a woman with three daughters and a man with three sons who met and married. Viewers who swore they had never been fans of either show somehow knew the lyrics, or at least couldn’t help associating phrases like a “three-hour tour” or “the youngest one in curls” with the two series.

Sherwood Charles Schwartz was born in Passaic, N.J., on Nov. 4, 1916. He grew up in Brooklyn and was a premed student at New York University. After receiving his bachelor’s degree, he moved to Los Angeles to attend graduate school at the University of Southern California, but the master’s he earned in biological sciences was never put to use.

In 1938, while waiting for acceptance to medical school, he asked his brother Albert, who worked on Bob Hope’s radio show, if he could try writing a few jokes. Soon there were two Schwartzes on Hope’s payroll.

After World War II, during which Sherwood Schwartz wrote for Armed Forces Radio, he became a writer for “The Adventures of Ozzie and Harriet,” which was then on the radio. He made the transition to television in the 1950s with the sitcom “I Married Joan” and “The Red Skelton Show,” for which he became head writer. In 1961 he shared an Emmy Award with his brother, Skelton and two other writers for the show.

In addition to his daughter, Mr. Schwartz is survived by his wife, Mildred; three sons, Lloyd, a television producer, Donald and Ross; eight grandchildren; and four great-grandchildren.

“Gilligan’s Island” began broadcasting in September 1964, with a cast that included Bob Denver as Gilligan, a bumbling first mate; Alan Hale Jr. as the skipper of the shipwrecked boat; and Jim Backus as Thurston Howell III, a millionaire, who managed to practice elitism while living in a hut. Guest stars turned up as British butterfly collectors, misguided aviators or headhunters in grass skirts, sometimes raising hope for the castaways’ rescue. But they were always left behind, even when the series ended in 1967.

The castaways finally did leave the island in a 1978 reunion special, “Rescue From Gilligan’s Island.” There were other specials; then, in 2004, the show was the inspiration for a reality series, “The Real Gilligan’s Island,” starring contestants whose real-life identities (millionaire, skipper and so on) matched those of the characters. As early as 1995 and as recently as this year, there was talk of a “Gilligan’s Island” feature film.

“The Brady Bunch” had its premiere in September 1969. It starred Florence Henderson and Robert Reed as clean-cut newlyweds with children whose most serious problems were usually on the level of sibling rivalry or a student council election.

The show lasted five seasons and, in a way, refused to die. After reruns proved enormously popular, there were three attempts at spinoff series (none lasted longer than half a season); a stage show, “The Real Live Brady Bunch,” in which original episodes of the series were re-enacted; and “The Brady Bunch Movie,” which had two sequels.

In interviews Mr. Schwartz talked about having intercepted a script for the first movie in which the Brady children used four-letter words. He told Paramount that he would personally campaign against the film if the language remained.

So when the first film, set in the 1990s, opened, the obliviously wholesome Bradys appeared to be living in a time warp, still dressing, talking and behaving as if it were the early ’70s. Apparently Mr. Schwartz had his way.