After graduating from South Boston's John A. Andrew Grammar School, McCarthy worked for a clothing company during the day and played baseball at night.

Setting aside aspirations of being a star pitcher, McCarthy finally settled into an everyday position in a lineup in 1888 with the St. Louis Browns in the American Association.

Although the shoddy record-keeping of the time prevents an accurate tally, he also asserted himself as a daring presence on the base-paths, by some accounts stealing over 100 bases in 1888 and approaching the mark in 1890.

After his playing career ended, McCarthy served as the head baseball coach at Holy Cross (1899–1900, 1904–1905, and 1916), Dartmouth (1906–1907), and Boston College (1920).

[1][2] McCarthy's selection into the Baseball Hall of Fame in 1946 has always been a controversial one due to his less than spectacular statistics, especially when compared to those of his fellow inductees and some players who have not yet been honored.

that he and his Boston teammates utilized, were a clever and gentlemanly counter to the rough and tumble "Baltimore" style of play which was, at the time, giving baseball a bad name.