Assuming that this is correct, the biggest shut out in history is 22-0. Detroit is currently leading the Royals 18-0 in the top of the eighth, with men on second and third, and two out.
[Update a couple minutes later]
They got one more run to end the inning. Going into the bottom of the eighth, it's 19-0. They scored ten runs in that inning. Three more in the ninth ties the record, and four breaks it. It could happen. Their bats seem pretty hot tonight, and Kansas City is deep into its bullpen. The Tigers just brought in Dolsi to preserve the shut out.
[Update a couple minutes later]
They blew it by relieving Miner. Dolsi let in a run on a wild pitch.
Dang.
[One more update]
Wow, they really blew it. The Royals got four runs in the bottom of the eighth off Dolsi and Lopez. Of course, once they lost the shut out, it didn't really matter. But people are going to be asking for a long time why Leland relieved out a pitcher who was pitching a three-hit shut out, with one who had an equivalent ERA.
[Update on Tuesday morning]
I guess I'd misread the box score. Miner had been replaced the inning before, before it looked like there was a history-making shut out to preserve.
Yeah, I was looking at this game, as well as the Dodgers-Rockies game. LA had 16 runs after the fifth inning. Both games had the potential to become 20-run games. Alas, neither did.
Oddly enough, I just finished compiling a list of historical 20-run games, merely to satisfy my own curiosity. I finished it on Sunday.
Pittsburgh beat the Chicago Cubs 22-0 on 9/16/1975, and Cleveland beat the N.Y. Yankees 22-0 on 8/31/2004.
The Yankees beat the Philadelphia Athletics 21-0 on 8/13/1939, and the Detroit beat Cleveland 21-0 on 9/15/1901.
That is the complete list of 20+ run shutouts after 1900.
Before 1900, there were a total of 14 such games. The highest scoring shutout of all time was Boston defeating Brooklyn 29-0 on 10/1/1874. That game was in the National Association, which predated the founding of the National League in 1876. In the 19th century, there were a total of 7 shutout games where the winner scored more than 22 runs.