Born in Bradford, Ohio, Sothoron threw and batted right-handed, stood 5 feet 11 inches (1.80 m) tall and weighed 182 pounds (83 kg).

His best season came in 1919, when he posted a 20–13 record with a 2.20 earned run average for the Browns, finishing fifth in the American League in wins and ERA.

His pitching career ended in St. Louis with the National League Cardinals, where he played for his first MLB manager, Branch Rickey, and led the NL in shutouts with four in 1924, despite a mediocre 10–16 (3.57) record.

In 1921, sportswriter Bugs Baer came up with this immortal quip: "Allen S. Sothoron pitched his initials off yesterday.

"[1] After his playing days, Sothoron managed in minor league baseball, coached for the Cardinals (1927), Boston Braves (1928), and Browns (1932–1933), and with the 1933 Browns he served a brief, eight-game managerial stint after the dismissal of Bill Killefer.