Contract bridge grand slam exists. The modern game of contract bridge was the result of innovations to the scoring of auction bridge by Harold Stirling Vanderbilt and others. The most significant change was that only the tricks contracted for were scored below the line toward game or a slam bonus, a change that resulted in bidding becoming much more challenging and interesting. Also new was the concept of "vulnerability", making sacrifices to protect the lead in a rubber more expensive. The various scores were adjusted to produce a more balanced and interesting game. Vanderbilt set out his rules in 1925, and within
American Contract Bridge League American Contract Bridge League The American Contract Bridge League (ACBL) is the governing body for contract bridge in the United States, Mexico, Bermuda and Canada and is a member of the World Bridge Federation, the international bridge governing body. It is the largest such organization in North America having the stated mission ""to promote, grow and sustain the game of bridge and serve the bridge-related interests of our Members."" Its major activities are: , it had more than 165,000 members. A not-for-profit organization, the ACBL was founded on December 23, 1937 in New York City and later moved its company