Usually it's the ninth inning because that's when teams rally from behind.
13
That was the 1st and the 4th where 8 runs combined were scored in each inning.
12
14
17 runs: Boston (17) vs. Detroit (0) on 6/18/1953
They scored 8 in the 2nd inning of some game. My source doesn't give the date, but that is the most they've scored in an inning this year.
The Cleveland Indians scored 14 runs in the top of the 2nd inning on April 18, 2009.
15
The most runs the Yankees have scored in one inning is 14in the 5th inning of a game against the Washington Nationals on July 6, 1920.
i believe it was the cardinals the other day who scored 9 in the 7t inning
Rickey Henderson.
The most runs scored in a single inning by the Baltimore Orioles was 12 against the Tampa Bay Devil Rays on April 11, 2002.