From BR Bullpen
A grand slam is a home run hit with runners on first, second, and third base. It is the ultimate hit in baseball as it scores four runs.
The all-time leaders in grand slams is Alex Rodriguez with 24 in his career, spent entirely in the American League, one more than Lou Gehrig, who also only played in the junior circuit. Willie McCovey is the National League leader with 18.
The single-season leaders with 6 grand slams each are Don Mattingly of the New York Yankees in 1987 and Travis Hafner of the Cleveland Indians in 2006. The National League record of 5 grand slams is shared by Ernie Banks of the Chicago Cubs in 1955 and Albert Pujols of the St. Louis Cardinals in 2009.
In the early days of baseball, a grand slam was often an inside-the-park home run, but nowadays that is exceedingly rare.
Many teams have hit two grand slams in one game, but on August 25, 2011, the New York Yankees became the first team in major league history to hit three. Robinson Cano, Russell Martin and Curtis Granderson all hit homers with the bases loaded in a 22-9 win over the Oakland A's.
 Two Grand Slams in a Game
The following players hit two grand slams in a game:
- Tony Lazzeri, May 24, 1936
- Jim Tabor, July 4, 1939
- Rudy York, July 27, 1946
- Jim Gentile, May 9, 1961
- Tony Cloninger, July 3, 1966
- Jim Northrup, June 24, 1968
- Frank Robinson, June 26, 1970
- Robin Ventura, September 4, 1995
- Chris Hoiles, August 14, 1998
- Fernando Tatis, April 23, 1999
- Nomar Garciaparra, May 10, 1999
- Bill Mueller, July 29, 2003
- Josh Willingham, July 27, 2009
Tatis hit his grand slams in the same inning, against the same pitcher (Chan Ho Park). One of Tabor's grand slams was an inside-the-park grand slam.
 Grand Slam in First Major League At-bat
Four players have hit a grand slam homer in their first big league plate appearance. They are:
- Bill Duggleby, April 21, 1898
- Jeremy Hermida, August 31, 2005
- Kevin Kouzmanoff, September 2, 2006
- Daniel Nava, June 12, 2010
 Grand Slam in the World Series
The following players have hit grand slam home runs in the World Series:
- Elmer Smith, 1920 Game 5
- Tony Lazzeri, 1936 Game 2
- Gil McDougald, 1951 Game 5
- Mickey Mantle, 1953 Game 5
- Yogi Berra, 1956 Game 2
- Bill Skowron, 1956 Game 7
- Chuck Hiller, 1962 Game 4
- Ken Boyer, 1964 Game 4
- Joe Pepitone, 1964 Game 6
- Jim Northrup, 1968 Game 6
- Dave McNally, 1970 Game 3
- Dan Gladden, 1987 Game 1
- Kent Hrbek, 1987 Game 6
- Jose Canseco, 1988 Game 1
- Lonnie Smith, 1992 Game 5
- Tino Martinez, 1998 Game 1
- Paul Konerko, 2005 Game 2