Collier came from one of America's prominent families. He was the son of Barron Gift Collier and Juliet Gordon Carnes, the founders of Collier County, Florida. He had two brothers, Miles Collier and Baron Collier Jr. As a teenager, Collier spent three seasons as designer, proprietor, and manager of the Overlook Theatre on the grounds of the Collier family estate in Pocantico Hills, New York. He began racing on a private course built on that estate — an early indication of the enthusiasm for motorsport that would shape the rest of his life. He attended Yale University, where he was a member of the Skull and Bones society, graduating in 1935. In 1936 he married Dixie Thompson from Honolulu; together they had three children: Samuel Carnes Collier Jr., Terry Collier, and Richard Collier.
Collier served in World War II as a Navy pilot. After the war, he channeled his competitive spirit into motor racing and business, helping to build the institutional framework for American sports car racing. He was one of the founders of the Automobile Racing Club of America, an organization that helped formalize and popularize the sport among enthusiasts and gentleman racers in the postwar United States. He also established Motor Sport, Inc., the sole American importer of MG cars, connecting American enthusiasts with British sports cars that were central to the road racing culture of the era. He had earlier competed in the 1939 Alpine Trial, a demanding European road event.
In 1949, Collier achieved a notable competitive result at Watkins Glen, New York, finishing third overall and first in Class E in the Seneca Cup Race while driving a supercharged MG. Watkins Glen, then a street circuit through and around the village, was one of the premier events on the American sports car calendar.
In 1950, Collier competed at the 24 Hours of Le Mans in one of two Cadillacs entered by Briggs Cunningham. The strictly stock saloon, co-driven by brothers Miles and Sam Collier, was nicknamed the "Clumsy Pup" by spectators due to its production-bodied appearance. The car finished tenth overall at an average speed of 81.398 miles per hour — a respectable result for a stock American saloon competing against purpose-built European machinery.
On September 23, 1950, Collier was killed while leading the Watkins Glen Grand Prix, an event held on public roads in and around the village of Watkins Glen, New York. The Ferrari 166 he was driving left the road, and he died later that evening at 6:30 pm in Montour Falls. The accident received front-page coverage in the New York press. A memorial stone was placed at the spot where his car left the road.
The loss affected American racing deeply. His brother Miles Collier gave up racing shortly after Sam's death, and Miles himself died of polio in 1954. Sam Collier was honored in 1995 in front of the Court House at that year's Watkins Glen Grand Prix Festival, a belated recognition of his role in establishing the circuit and sport that had claimed his life.
Sam Collier's contributions to American motor racing extended well beyond his on-track results. As a co-founder of the Automobile Racing Club of America and a key importer of British sports cars, he helped lay the groundwork for the organized road-racing scene that flourished in the United States through the 1950s and beyond. The Watkins Glen circuit that hosted his fatal accident went on to become one of the most celebrated road racing venues in North American motorsport history, eventually hosting the United States Grand Prix. Collier belongs to the generation of wealthy American enthusiasts who transformed a hobby into an institution.