Calvin Shepherd was born in Port Arthur, Texas, and graduated from Lincoln High School in 1970. Soon after graduation, he enlisted in the United States Marine Corps, where he served honorably as a Private First Class Machine Gunner during the Vietnam War.

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During his military service, Shepherd distinguished himself not only as a Marine but also as an elite athlete. He earned the National Defense Service Medal and an All-Marine Certificate, recognizing his dedication and performance. While serving, he developed a passion for boxing and quickly rose through the Marine Corps ranks, capturing the All-Marine Boxing Championship title. His success in the ring extended beyond the military—he was later named both the All-Hawaiian Boxing Champion and the All–Southern and North Dakota Boxing Champion, solidifying his reputation as a powerful and disciplined competitor.

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After his service, Shepherd pursued professional boxing under the guidance of his longtime manager and trainer, Dick Menchaca, a well-known figure in the Port Arthur boxing community. In 1983, at the age of 30, Shepherd achieved the pinnacle of his career by winning the World Athletic Association (WAA) Bantamweight Championship. He secured the title with a technical knockout in the seventh round against Mondo Loredo of Corpus Christi—a defining moment in his professional journey.

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Over the course of his career, Shepherd fought on four world title fight cards and earned recognition for his resilience, discipline, and sportsmanship. His record reflected both his skill and endurance in a highly competitive era of boxing.

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For his accomplishments, Shepherd was inducted into the Museum of the Gulf Coast Sports Hall of Fame in 2008, and later into the All-Marine Boxing Hall of Fame in 2017, honoring both his military and athletic excellence.