In 1886, the St. Louis Browns won the American Association championship with a record of 93–46, while the Chicago White Stockings won the National League championship with a record of 90–34. The two teams agreed to meet each other in a best-of-seven pre-modern-era World Series, with the winner taking all the prize money. It was the second straight year that the Browns and White Stockings met in the World Series. The six games of the series were played on six consecutive days.
October 18: The series started in Chicago. White Stockings pitcher John Clarkson threw a five-hit shutout to beat the Browns, 6–0.
October 19: The Browns won 12–0 in a game shortened to eight innings due to darkness. St. Louis pitcher Bob Caruthers allowed one hit, and Tip O'Neill hit two home runs.
October 20: Caruthers asked to pitch for the second day in a row, and he lost to Clarkson and the White Stockings, 11–4, in eight innings.
October 21: The series moved to St. Louis, and Clarkson pitched for the third time in four days. The game was tied 5–5 until the Browns scored three runs in the sixth inning to win, 8–5. It was called after seven innings.
October 23: Caruthers started the game for St. Louis, while Clarkson started for Chicago. The White Stockings led 3–0 until the eighth inning, when the Browns scored three runs to tie the game. With one out in the bottom of the tenth, the Browns' Curt Welch was on third base when Clarkson threw a pitch that got by catcher King Kelly. Welch scored, and St. Louis won the game, 4–3, and the series, four games to two. It is disputed whether or not Welch slid across the plate, but the play was known as the "$15,000 slide" and was the most famous play in 19th-century baseball.
The Browns' O'Neill led all players with a .400 batting average, eight hits, and two home runs in the series. Welch had the second-highest batting average, at .350. Caruthers, who started three games for St. Louis, went 2–1 with a 2.42 earned run average. Clarkson started four games for Chicago and went 2–2 with a 2.03 ERA.
For winning the series, St. Louis earned $13,920 in prize money. This was the American Association's only undisputed championship over the National League.