Schulz loved drawing and sometimes drew his family dog, Spike, who ate unusual things, such as pins and tacks. In 1937, Schulz drew a picture of Spike and sent it to Ripley’s Believe It or Not!; his drawing appeared in Robert Ripley’s syndicated panel, captioned, “A hunting dog that eats pins, tacks, and razor blades is owned by C. F. Schulz, St. Paul, Minn.” and “Drawn by ‘Sparky'” (C.F. was his father, Carl Fred Schulz).

In February 1943, Schulz’s mother Dena died after a long illness. At the time of her death, he had only recently been made aware that she suffered from cancer. Schulz had by all accounts been very close to his mother and her death had a significant effect on him.

In late 1945, Schulz returned to Minneapolis. He did lettering for a Roman Catholic comic magazine, Timeless Topix, and in July 1946 took a job at Art Instruction, Inc., where he reviewed and graded students’ work. Schulz had taken a correspondence course from the school before he was drafted. He worked at the school for several years as he developed his career as a comic creator.

Schulz’s first group of regular cartoons, a weekly series of one-panel jokes called Lil’ Folks, was published from June 1947 to January 1950 in the St. Paul Pioneer Press, with Schulz usually doing four one-panel drawings per issue. It was in Li’l Folks that Schulz first used the name Charlie Brown for a character, although he applied the name in four gags to three different boys as well as one buried in sand. The series also had a dog that looked much like Snoopy. In May 1948, Schulz sold his first one-panel drawing to The Saturday Evening Post; within the next two years, a total of 17 untitled drawings by Schulz were published in the Post, simultaneously with his work for the Pioneer Press. Around the same time, he tried to have Li’l Folks syndicated through the Newspaper Enterprise Association; Schulz would have been an independent contractor for the syndicate, unheard of in the 1940s, but the deal fell through. Li’l Folks was dropped from the Pioneer Press in January 1950.

Later that year, Schulz approached United Feature Syndicate with the one-panel series Li’l Folks, and the syndicate became interested. By that time Schulz had also developed a comic strip, usually using four panels rather than one, and to Schulz’s delight, the syndicate preferred that version. Peanuts made its first appearance on October 2, 1950, in seven newspapers. The weekly Sunday page debuted on January 6, 1952. After a slow start, Peanuts eventually became one of the most popular comic strips of all time, as well as one of the most influential. Schulz also had a short-lived sports-oriented comic strip, It’s Only a Game (1957–59), but he abandoned it after the success of Peanuts. From 1956 to 1965 he contributed a gag cartoon, Young Pillars, featuring teenagers, to Youth, a publication associated with the Church of God.

In April 1951, Schulz married Joyce Halverson (no relation to Schulz’s mother Dena Halverson Schulz), and Schulz adopted Halverson’s daughter, Meredith. Later the same year, they moved to Colorado Springs, Colorado. Their son, Monte, was born in February 1952, and three more children were born later, in Minnesota.

The first collection of Peanuts strips was published in July 1952 by Rinehart & Company. Many more books followed, greatly contributing to the strip’s increasing popularity. In 2004, Fantagraphics began their Complete Peanuts series. Peanuts also proved popular in other media; the first animated TV special, A Charlie Brown Christmas, aired in December 1965 and won an Emmy award. Numerous TV specials followed, the latest being Happiness is a Warm Blanket, Charlie Brown in 2011. Until his death, Schulz wrote or co-wrote the TV specials and carefully oversaw their production.

In 1957 and 1961 he illustrated two volumes of Art Linkletter’s Kids Say the Darndest Things, and in 1964 a collection of letters, Dear President Johnson, by Bill Adler.

Schulz received the National Cartoonists Society’s Humor Comic Strip Award in 1962 for Peanuts, the Society’s Elzie Segar Award in 1980, and was also the first two-time winner of their Reuben Award for 1955 and 1964, and their Milton Caniff Lifetime Achievement Award in 1999. He was also an avid hockey fan; in 1981, Schulz was awarded the Lester Patrick Trophy for outstanding contributions to the sport of hockey in the United States, and he was inducted into the United States Hockey Hall of Fame in 1993. On June 28, 1996, Schulz was honored with a star on the Hollywood Walk of Fame, adjacent to Walt Disney’s. A replica of this star appears outside his former studio in Santa Rosa. Schulz is a recipient of the Silver Buffalo Award, the highest adult award given by the Boy Scouts of America, for his service to American youth.

Schulz and his family returned to Minneapolis and stayed until 1958. They then moved to Sebastopol, California, where Schulz built his first studio. (Until then, he’d worked at home or in a small rented office room.) It was there that Schulz was interviewed for the unaired television documentary A Boy Named Charlie Brown. Some of the footage was eventually used in a later documentary, Charlie Brown and Charles Schulz. Schulz’s father died while visiting him in 1966, the same year Schulz’s Sebastopol studio burned down. By 1969, Schulz had moved to Santa Rosa, California, where he lived and worked until his death. While briefly living in Colorado Springs, Schulz painted a mural on the bedroom wall of his daughter Meredith, featuring Patty with a balloon, Charlie Brown jumping over a candlestick, and Snoopy playing on all fours. The wall was removed in 2001, donated and relocated to the Charles M. Schulz Museum in Santa Rosa.

Schulz had a long association with ice sports, and both figure skating and ice hockey featured prominently in his cartoons. In Santa Rosa, he owned the Redwood Empire Ice Arena, which opened in 1969 and featured a snack bar called “The Warm Puppy”. Schulz’s daughter Amy served as a model for the figure skating in the television special She’s a Good Skate, Charlie Brown (1980). Schulz also was very active in senior ice-hockey tournaments; in 1975, he formed Snoopy’s Senior World Hockey Tournament at his Redwood Empire Ice Arena, and in 1981, he was awarded the Lester Patrick Trophy for outstanding service to the sport of hockey in the United States. Schulz also enjoyed golf and was a member of the Santa Rosa Golf and Country Club from 1959 to 2000.

A proponent of manned spaceflight, Schulz was honored with the naming of Apollo 10 command module Charlie Brown and Lunar Module Snoopy, launched on May 18, 1969. The Silver Snoopy award is a special honor awarded to NASA employees and contractors for outstanding achievements related to human flight safety or mission success. The award certificate states that it is “In Appreciation” “For professionalism, dedication and outstanding support that greatly enhanced space flight safety and mission success.”

By Thanksgiving 1970, it was clear that Schulz’s marriage was in trouble. He was having an affair with a 25-year-old woman named Tracey Claudius. The Schulzes divorced in 1972, and in September 1973 he married Jean Forsyth Clyde, whom he had first met when she brought her daughter to his hockey rink. They were married for 27 years, until Schulz’s death in 2000.

On January 1, 1974, Schulz served as the Grand Marshal of the Rose Parade in Pasadena, California. The same year, he received the Inkpot Award. In 1980, Schulz received the Golden Plate Award of the American Academy of Achievement presented by Awards Council member Judge John Sirica.

In July 1981, Schulz underwent heart bypass surgery. During his hospital stay, President Ronald Reagan phoned to wish him a quick recovery.

On July 1, 1983, Camp Snoopy opened at Knott’s Berry Farm, a forested, mountain theme area featuring the Peanuts characters. It has rides designed for younger children and is one of the most popular areas of the amusement park.

When the Mall of America in Bloomington, Minnesota, opened in 1992, the amusement park in the center of the mall was themed around Schulz’s Peanuts characters until the mall lost the rights to use the brand in 2006.

The Charles M. Schulz Museum counts Milton Caniff (Terry and the Pirates) and Bill Mauldin as key influences on Schulz’s work. In his own strip, Schulz regularly described Snoopy’s annual Veterans Day visits with Mauldin, including mention of Mauldin’s World War II cartoons. Schulz (and critics) also credited George Herriman (Krazy Kat), Roy Crane (Wash Tubbs), Elzie C. Segar (Thimble Theatre) and Percy Crosby (Skippy) as influences. In a 1994 address to fellow cartoonists, Schulz discussed several of them. But according to his biographer Rheta Grimsley Johnson:

At its height, Peanuts was published daily in 2,600 papers in 75 countries, in 21 languages. Over nearly 50 years, Schulz drew 17,897 published Peanuts strips. The strips, plus merchandise and product endorsements, produced revenues of more than $1 billion per year, with Schulz earning an estimated $30 million to $40 million annually. During the strip’s run, Schulz took only one vacation, a five-week break in late 1997 to celebrate his 75th birthday; reruns of the strip ran during his vacation, the only time that occurred during Schulz’s life.

Schulz was a keen bridge player, and Peanuts occasionally included bridge references. In 1997, according to Alan Truscott, the American Contract Bridge League (ACBL), awarded both Snoopy and Woodstock the honorary rank of Life Master, and Schulz was delighted. According to the ACBL, only Snoopy was awarded the honor.

In 1998, Schulz hosted the first Over 75 Hockey Tournament. In 2000, the Ramsey County Board in St. Paul, Minnesota voted to rename the Highland Park Ice Arena the Charles M. Schulz–Highland Arena in his honor.

In November 1999, Schulz suffered several small strokes and a blocked aorta, and he was later found to have colon cancer that had metastasized. Because of the chemotherapy and the fact that he could not see clearly, he announced his retirement on December 14, 1999. This was difficult for Schulz, who told Al Roker on The Today Show, “I never dreamed that this was what would happen to me. I always had the feeling that I would probably stay with the strip until I was in my early eighties. But all of a sudden it’s gone. It’s been taken away from me. I did not take this away from me.”

Schulz died at his home on February 12, 2000, at the age of 77, of colon cancer. The last original Peanuts strip was published the next day. He had predicted that the strip would outlive him because the strips were usually drawn weeks before their publication. Schulz was buried at Pleasant Hills Cemetery in Sebastopol, California.

Schulz was honored on May 27, 2000, by cartoonists of more than 100 comic strips, who paid homage to him and Peanuts by incorporating his characters into their strips that day.

On February 10, 2000, two days before Schulz’s death, Congressman Mike Thompson introduced H.R. 3642, a bill to award Schulz the Congressional Gold Medal, the highest civilian honor the United States legislature can bestow. The bill passed the House (with only Ron Paul voting no and 24 not voting) on February 15, and the bill was sent to the Senate where it passed unanimously on May 2. The Senate also considered the related bill, S.2060 (introduced by Dianne Feinstein). President Bill Clinton signed the bill into law on June 20, 2000. On June 7, 2001, Schulz’s widow Jean accepted the award on behalf of her late husband in a public ceremony.

The Jean and Charles Schulz Information Center at Sonoma State University opened in 2000 and now stands as one of the largest buildings in the CSU system and the State of California, with a 400,000-volume general collection and with a 750,000-volume automated retrieval system capacity. The $41.5 million building was named after Schulz, and his wife donated the $5 million needed to build and furnish the structure.

In 2000, the Sonoma County Board of Supervisors renamed the county airport as the Charles M. Schulz–Sonoma County Airport in the cartoonist’s honor. The airport’s logo features Snoopy in goggles and scarf, taking to the skies on top of his red doghouse.

Peanuts on Parade has been St. Paul, Minnesota’s tribute to its favorite native cartoonist. It began in 2000 with the placing of 101 5-foot-tall (1.5 m) statues of Snoopy throughout the city of St. Paul. Every summer for the following four years, statues of a different Peanuts character were placed on the sidewalks of St. Paul. In 2001, there was Charlie Brown Around Town, 2002 brought Looking for Lucy, in 2003 along came Linus Blankets St. Paul, ending in 2004 with Snoopy lying on his doghouse. The statues were auctioned off at the end of each summer, so some remain around the city, but others have been relocated. The auction proceeds were used for artist’s scholarships and for permanent, bronze statues of the Peanuts characters. These bronze statues are in Landmark Plaza and Rice Park in downtown St. Paul.

The Charles M. Schulz Museum and Research Center in Santa Rosa opened on August 17, 2002, two blocks away from his former studio, celebrating his life’s work and the art of cartooning. A bronze statue of Charlie Brown and Snoopy stands in Depot Park in downtown Santa Rosa.

Santa Rosa, California, celebrated the 60th anniversary of the strip in 2005 by continuing the Peanuts on Parade tradition beginning with It’s Your Town, Charlie Brown (2005), Summer of Woodstock (2006), Snoopy’s Joe Cool Summer (2007), and Look Out For Lucy (2008).

In 2006, Forbes ranked Schulz as the third-highest-earning deceased celebrity, as he had earned $35 million in the previous year. In 2009, he was ranked sixth. According to Tod Benoit, in his book Where Are They Buried? How Did They Die?, Charles M. Schulz’s income during his lifetime totaled more than $1.1 billion.

Schulz was inducted into the United States Figure Skating Hall of Fame in 2007.