Through the 2013 season, there were 6452 grand slams hit in baseball history. The most grand slams in a season happened in the year 2000 when 176 grand slams were hit.
Alex Rodriguez hit 3 grand slams during the 2007 season.
Don Mattingly hit six grand slams in his career. They were all hit during the 1987 season.
6, accomplished by Lou Gehrig and Travis Hafner
Alex Rodriguez has hit three grand slams during the 2010 season.
That was the 1987 season. Incredibly, he wound up his career with six total grand slams, all in the 1987 season.
two grand slams
Lou Gehrig with 23