1stIn Philadelphia, the greatest crowd in baseball history, 30,000, gather to watch the first match in a home-and-home series between the champion Atlantics from Brooklyn and the Athletics of Philadelphia. Batting first, the A’s score a pair but the press of the crowd makes play impossible and the game is called.
11th The visiting Star Club loses to the Atlantic Club by a 46–18 score. The game is played in one hour, 50 minutes, with not a ball or a strike called. According to the rules of the day, the ump must warn the batter before calling a strike.
15thBefore a crowd of 18,000, the Atlantics host the Athletics, beating them, 27–17, behind pitcher Tom Pratt and hitter Joe Start. Start scores 6 runs. Game stats include Errors of Fielding show that the Atlantics make 10 errors while the Athletics have 44!
22ndIn Philadelphia, 20,000 show up for the rematch between the Atlantics and the Athletics. This time the A’s overwhelm the visitors, 31–12, in a rain-shortened 7 innings. Because of a disagreement over dividing the gate receipts, no rubber game is played.
27thIn Philadelphia, the Unions of Morrisania, with George Wright playing shortstop, upset the Athletics, 42–29.
29thThe final championship match of the season is between the Irvington (NJ) club and host Atlantics, with the 2 clubs playing a rubber match to determine the champion of 1866. The Atlantics break a 5–5 tie by scoring 7 in the 10th inning and winning, 12–6 to keep the Championship.