The modern game of contract bridge was the result of innovations to the scoring of auction bridge made by Harold Stirling Vanderbilt and others. The most significant change was that only the tricks contracted for were counted below the line towards game and slam.
Contract bridge as a distinct game emerged from the developments made to the scoring rules of auction bridge by Harold Stirling Vanderbilt and other experts. A crucial change was that only the agreed-upon tricks were taken into account in determining game and slam triumphs.