October 15 – Denny McKnight organizes the Allegheny Baseball Club of Pittsburgh in anticipation of playing in the new American Association. The team, still in existence today, will become known as the Pittsburgh Pirates.
October 10 – Initiated by backers of the new Cincinnati Red Stockings club, the first meetings are held in Pittsburgh of what would become the American Association.
October 8 – Chris von der Ahe takes control of the St. Louis Browns. The Browns join the soon to be formed American Association, become a dominant team and eventually join the National League and still exist today as the St. Louis Cardinals.
September 29 – The National League issues a list of 10 blacklisted players who will require unanimous league approval for reinstatement. The reason given for the blacklisting is “confirmed dissipation and general insubordination.”
September 27 – The Troy Trojans lose to the champion Chicago White Stockings 10–8 in a heavy rain storm in front of 12 spectators, setting a record for the least attended game.
September 25 – The National League announces that all 8 teams will return for the 1882 season. This is the first time that the major leagues have had the same teams in 2 consecutive seasons.
Ed Nolan‚ John Clapp‚ and Jim McCormick all miss the Cleveland game in Worcester because their return from a side trip to NYC is delayed by a t rain wreck. The club fines each $100. The Blue Stockings win without them‚ 6-5.
9/17/1881: For the second time, Worcester’s Fred Corey, playing right field, lost a homer when he failed to touch third. This time it was against Cleveland in the ninth inning of a 7-2 win. These would have been the first two homers in his career, which ended up with a total of seven.
September 16 – The Chicago White Stockings win their 2nd straight pennant with a 4–0 win over the Boston Red Caps.
September 15 – Davy Force of the Buffalo Bisons turns 2 unassisted double plays, participates in 2 other double plays and starts a triple play for the Bisons. Despite his feat, Buffalo loses in 12 innings, 7–6 to the Worcester Ruby Legs.