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.
Alex Rodriguez has hit three grand slams during the 2010 season.
6, accomplished by Lou Gehrig and Travis Hafner
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
14, by the Oakland Athletics in 2000 and the Cleveland Indians in 2006.
Andre ethier has hit 2 grand slams so far
williams Ted Williams is the career grand slam leader for the Red Sox with 17. The single season grand slam leader for the Red Sox is Babe Ruth who hit 4 in 1919.
Barry Bonds hit eleven grand slams during his career.
Unfortunately, the most recent data I could find was for the 2008 MLB season. In 2008, 124 grand slams were hit (72 in the AL and 52 in the NL) in 2428 total games for an average of 1 grand slam every 19.58 games. The most grand slams hit in an MLB season is 176 (89 in the AL and 87 in the NL) in 2429 games in the 2000 season for an average of 1 grand slam every 13.80 games.
For his entire career he hit 6 grand slams and oddly enough they all were hit in 1987.
Robin Yount hit three career grand slam home runs, 2 in the 1980 season and 1 in the 1984 season.
Lou Gehrig hit 23 Grand Slams during his career, which is a MLB record.