Baker's legacy has grown over the years, and he is regarded by many as the best third baseman of the pre-war era. During his 13 years as a Major League player, Baker never played a single inning at any position other than third base. Baker was elected to the National Baseball Hall of Fame in 1955.
Baker was born in Trappe, Maryland. He enjoyed working on his father's farm, but he aspired become a professional baseball player from the age of ten. In Trappe, most of the residents attended the local baseball team's games on Saturdays. Frank's older brother Norman was well known in the town for his playing ability and once tried out for the Philadelphia Athletics, but he did not like that city and stopped pursuing a baseball career.
Baker pitched for the local high school baseball team and worked as a clerk at a butcher shop and grocery store owned by relatives. He signed with a local team in Ridgely at the age of 19. The team, which was managed by Buck Herzog, paid him $5 per week and covered his boarding costs. Herzog found that Baker could not pitch well, but that he could hit. Baker was unable to play the outfield well, but he was able to move into the infield as a third baseman for Ridgely.
In seven seasons with the A's he hit .321 with 48 home runs, 612 RBIs and 88 triples in 866 games played.
Baker played third base for the Athletics until 1915, when he sat out the entire season in a contract dispute with Connie Mack. He remained in baseball, playing for Upland, Pennsylvania in the semiprofessional Delaware County League.
Mack sold Baker's contract in 1916 to the New York Yankees, with whom he finished his career. Baker and Wally Pipp formed the center of the Yankees' batting order. Pipp led the American League in home runs with 12 in 1916; Baker finished second with 10. Pipp hit nine home runs in 1917, again leading the league. Baker led the league with 141 games played in 1919.
Baker retired for one season in 1920, but came back to play two more years with the Yankees (and in their first two World Series as well), finishing as a Yankee with a .288 batting average, 48 home runs and 375 RBIs in 676 games.
Baker and his wife had twin babies in late January 1914. The babies were reported as doing well a couple of days later, but they died before they were two weeks old. The twins were initially reported as a boy and a girl by The New York Times, but they were reported as twin girls by the same publication a few days later.
^Lanctot, Neil (1994). Fair Dealing and Clean Playing: the Hilldale Club and the development of black professional baseball, 1910-1932. Jefferson, NC: McFarland. p. 11. ISBN0-89950-988-6.
"Semiprofessional" may be a euphemism. Upland employed other major leaguers between 1915 and 1919 (including Baker's longtime teammate Chief Bender), and by 1919 the Delaware County League was declared an outlaw league by organized baseball.