 He played six seasons in Major League Baseball with the Milwaukee Brewers (1884), Detroit Wolverines (1885–1888), Brooklyn Bridegrooms (1890), and Buffalo Bisons (1890).Baldwin had his best season in 1886 when he compiled a 42–13 record and a 2.24 earned run average (ERA), threw 55 complete games, and led the National League with 323 strikeouts.Baldwin's 42 wins in 1886 set the major league record for a left-handed pitcher and remains the second highest single season total by a southpaw.