Because his father traveled extensively, young McCarthy attended schools in a dozen different cities.
In 1896, McCarthy saw his first Kentucky Derby, and until his fifteenth birthday aspired to be a jockey. After being convinced he was too large for the job, he began his professional career as a handicapper and race reporter for a San Diego newspaper. His constant exposure to horses and racing, and several years of experience as an auctioneer, prepared him for his later career. In 1927, McCarthy was hired to be the voice on the public address system at Chicago's Arlington Park. There he was able to utilize both his extensive knowledge of horses and racing and the trained voice he had developed during his days as an auctioneer. In 1928 radio station KYW in Chicago hired him to broadcast the first Kentucky Derby ever heard on radio. The following year he joined the National Broadcasting Company (NBC) and began announcing some of the nation's major sporting events, including the Kentucky Derby, the Preakness, and several world championship boxing matches.
By the early 1930's McCarthy's voice was associated with horse racing and boxing events everywhere there were radios, and his announcement "R-r-r-racing fans" became an American institution. With binoculars in one hand and the microphone in the other, McCarthy covered thousands of horse races. He broadcast the Grand National Steeplechase from England; he provided the radio accounts of all the leading races at Saratoga; he broadcast the Meadowbrook polo matches; he was a sports commentator for WMCA in New York; he wrote articles on racing for both dailies and turf publications; he had a syndicated column carried in several newspapers; and he did Path newsreels. McCarthy's command of words and the speed with which he followed the progress of fights and races made him very popular with his listening audience. Probably his two most exciting broadcasts were both aired in 1938: the return bout between Joe Louis and Max Schmeling "Schmeling is down! Schmeling is down!" and the duel between War Admiral and Seabiscuit in a "match race" They've got 200 yards to come.
During his career he memorized more than 200 racing colors. This knowledge, along with his "throaty and gravelly machine-gun voice, " kept audiences attentive to his every word. McCarthy not only helped sell many radios but also brought the thrill and drama of American sports to more people than ever before. McCarthy left NBC in 1947 and joined the Columbia Broadcasting System (CBS). He covered the Kentucky Derby for CBS through 1950, ending his "affair" with Churchill Downs after twenty-three consecutive broadcasts. His last assignments, during the early 1950's, were broadcasts from the meets at Roosevelt Raceway for New York City stations.
In May 1957 McCarthy was seriously injured in a car crash. He was awarded $85, 000 in a lawsuit, but after all debts were paid, he was left penniless in a nursing home in New York City. In 1961 several announcers established the Clem McCarthy Fund to help defray his expenses. The William Black Foundation agreed to contribute matching funds. The following year a record, "Clem McCarthy, the Voice of American Sports, " was cut at the expense of Riverside Record Company, NBC, and Ed Sullivan, who supplied the introduction and commentary. Proceeds from sales were to go to McCarthy, but he died the following month in New York City.
Radio listeners appreciated McCarthy's style, which made them feel as if they were actually witnessing the event. He often spent days before a race getting to know horses, trainers, and jockeys. He had a reputation for accuracy, but made a memorable blunder in 1947, when he called the wrong winner for the Preakness. After realizing his mistake, McCarthy immediately corrected himself: "All right, we missed, we struck out. Well Babe Ruth struck out, so I might just as well get in famous company. "
In 1929, McCarthy married Vina Smith, a vaudeville actress. They had no children. His wife, who had been ill with cancer, died in 1949 after draining much of McCarthy's savings for medical treatment.