William Harold Southworth (March 9, 1893 - November 15, 1969) was an American right fielder, center fielder and manager in Major League Baseball (MLB). Playing in 1913 and 1915 and from 1918 to 1929, he batted left-handed and threw right-handed. Southworth managed in 1929 and from 1940 through 1951.

Southworth was born in Harvard, Nebraska, to Orlando and Marriah Southworth. He was raised in Columbus, Ohio. He had four older brothers who played baseball. Before he was old enough to play with them, Southworth would give his old socks to his brothers so they could create makeshift balls. Southworth decided to play baseball against his father's wishes. Orlando Southworth had wanted his son to attend college. At the age of 19, he signed a contract with the Portsmouth team in the Ohio State League. He joined the Cleveland Indians in 1913, but only appeared in one game, entering as a replacement on defense.  In 1914, Southworth married Lida Brooks. She was a minister's daughter and they had met while Southworth was playing for Portsmouth. The couple's son, William Brooks Southworth, was born during Southworth's early playing career. Billy Southworth, Jr. later became a professional baseball player for several seasons. The elder Southworth returned to the Cleveland Indians in 1915 and appeared in 60 games. He played for the Birmingham Barons in 1917 and part of 1918, when he made the Pittsburgh Pirates and played in 64 major league games.  Southworth played more regularly in 1919, appearing in 121 games and leading the league with 14 triples. With the exception of two seasons, Southworth played in at least that many games through 1926. In 1926, Southworth's offensive production increased and he finished the season with a .320 batting average, 16 home runs and 99 RBI. He ran into difficulty with New York manager John McGraw that year, as Southworth's independent style became incompatible with McGraw's strict leadership. He was traded from the New York Giants to the St. Louis Cardinals in the middle of the season. Southworth suffered a 1927 rib injury that limited his playing time. The Cardinals' leadership began to look for a role for Southworth beyond his playing career.

Using a quote from the above article, answer the following question: When did he start playing?
At the age of 19, he signed a contract with the Portsmouth team in the Ohio State League.