William Thomas Overgard (April 30, 1926 – 1990), was born in Santa Monica, California, son of silent-movie actor William A. Overgard, and grew up there. Inspired as a boy by Milton Caniff's Terry and the Pirates, at age twelve he sent him a fan letter and samples of his own art, and received encouragement. They continued corresponding during Overgard's high school years and two years in the Navy during World War II. Afterwards, he headed for New York and worked with Caniff, assisting him on his new strip Steve Canyon. He later regarded this apprenticeship as his only true training for cartooning. Then, on Caniff's advice, he launched his own cartooning career in the 1950s with comic books such as Jungle Jim, Ben Bowie, Daredevil, and the western Black Diamond. He also freelanced in ghosted strips and animation, continuing to refine his artwork, and contributed to Boy Magazine and the satirical Whack.

In 1954, Steve Roper artist Pete Hoffman was leaving to do his own strip, Jeff Cobb. As recalled by Harvey 2004, Overgard had been trying to get a syndicated gig, and when the Roper job opened up, he was invited to compete with other candidates for the assignment. 'Fortunately,' he wrote, 'I managed to scoot by and win, and that was the beginning of my career as a strip cartoonist. 'The first strip he drew for Steve Roper was for July 12, 1954. When the writer, Allen Saunders, was considering a counterfoil pal for 'straight-arrow' Roper, Overgard suggested a character he had been working on and described as 'a realistic working-man kind of guy who was not beyond taking any opportunity that presented itself', as noted by Harvey. Thus appeared on June 19, 1956, Mike Nomad, who would ultimately become the protagonist of the strip.

With a family started and the security of Steve Roper, in 1954 Overgard and his wife Gloria 'left behind their bohemian Manhattan life' and moved up the Hudson to a house on a rural 17-acre (69,000 m2) site in Stony Point, NY, close to friend Caniff's home. He invested much of his earnings over the years in renovating the house built in 1770 while also indulging a love of antique cars and motorcycles. He did his cartooning and writing at night, except when he and his wife entertained in 'artsy soirees' in their home and gardens.

In 1963, May 17, he wrote in Time Magazine that a featured painting by pop artist Roy Lichtenstein 'came close' to an August 6, 1961 panel of his Steve Roper. He added: 'Very flattering... I think?' He joined the National Cartoonists Society and clearly took pride in his work on the strip which became Steve Roper and Mike Nomad in 1969, giving it new popularity.

In 1971 Overgard also took on the scripting of Kerry Drake after Saunders quit, and as that strip ended, began a new one he both wrote and drew, Rudy, which debuted on January 3, 1983. By then, there were disagreements over the writing of Steve Roper with Allen Saunders and son John who succeeded him in 1979. After his strip for April 7, 1985, Overgard left Steve Roper, immediately replaced by Fran Matera, and devoted himself to Rudy. Despite favorable reviews, Rudy came to an end later that year on December 22.

Overgard had already expanded into screenplays and televised cartoons, now scripting episodes of ThunderCats. He had also been writing adventure novels, and in 1988 published his last one, A Few Good Men, about the U.S. Marines' 1931 intervention in the Sandinista war in Nicaragua. He continued his longtime interests in antique cars and music-making, especially the banjo. He died in Stony Point on May 25, 1990, survived by wife Gloria, sons Tom and Matthew, and daughter Jennifer Magnusson, and leaving an archive of his earlier Steve Roper work at Syracuse University.