With the Astros' 3-2 win over the Red Sox on Friday, they joined the Dodgers and Indians in reaching the 100-victory mark, making 2017 the sixth season in Major League history in which three teams have won 100 games.
The most recent instance came in 2003, when the Yankees, Braves and Giants accomplished the feat. It also happened in 2002 (Yankees, Athletics and Braves), 1998 (Yankees, Braves, Astros), 1977 (Yankees, Royals, Phillies) and 1942 (Yankees, Cardinals, Dodgers).

The 2017 season is the first of the six instances that doesn't include the Yankees, who have reached the milestone 19 times since their inaugural season in 1903. After a 4-0 win over Toronto on Friday, New York sits at 90-70.
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Prior to this season, baseball had seen only three teams reach 100 victories since 2010 -- the '11 Phillies (102-60), the '15 Cardinals (100-62) and last season's Cubs (103-58).
In the five previous years with three 100-game winners, three teams went on to win the World Series -- the 1998 and '77 Yankees and, back when the postseason was only one round, the '42 Cardinals. Two other teams, the 1942 and 2003 Yankees, made it to the Fall Classic but lost.
Reaching the century mark in the win column is a notable achievement for these three clubs on their own. The Astros have only done it once before as part of 1998's 100-win trio. It's the seventh such season for the Dodgers, (1899, 1941, '42, '53, '62, and '74) and the third for the Indians (1954 and '95).