- Oct 2 Cincinnati Reds and Pittsburgh Pirates play first and only MLB triple header in the 20th century; Reds win the first two games, 13-4 and 7-3; Pirates avoid the sweep in the finale, 6-0
- Oct 3 American Pro Football Association (later the NFL) plays 1st full round of games; Dayton Triangles beat Columbus Panhandles, 14-0 in first official game at Triangle Park, Dayton
- Oct 3 St Browns 1st baseman George Sisler collects his 257th hit of the season to set MLB record that lasts until the 21st century.; Browns beat White Sox, 16 - 7
- Oct 6 1st brothers oppose each other in World Series, Cleveland's Wheeler Johnston pinch-hits as brother Jimmy plays 3rd base for Brooklyn
- Oct 10 Cleveland Indians outfielder Elmer Smith hits baseball's first ever World Series grand slam and teammate Bill Wambsganss makes the 1st unassisted World Series triple play (Game 5)
- Oct 10 Phoenix Cardinals (then in Chicago) play 1st NFL game, a 0-0 tie
- Oct 12 Baseball World Series: Cleveland Indians beat Brooklyn Robins, 8-1 at League Park for a 5 games to 2 series victory; Indians first Championship
- Oct 13 World Series celebration in Wade Park brings out 50,000+ Clevelanders
- Oct 17 Decatur Staleys, later known as Chicago Bears, play 1st American Professional Football Association game against an affiliated APFA team; beat Rock Island Independents, 7-0 at Douglas Park, Rock Island, Illinois
- Oct 23 Chicago grand jury indicts Abe Attell, Hal Chase, & Bill Burns as go-betweens in "Black Sox" 1919 World Series Baseball scandal
- Oct 29 Ed Barrow appointed GM of NY Yankees
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