A brief history of contract bridge can be viewed on the ABF website in the ABF New Member's Information Kit - look under Resources.
Essentially, the modern version of our game occurred as a refinement to the rules of an older version called auction bridge.
Harold S Vanderbilt (6 July 1884 - 4 July 1970) of Newport, Rhode Island is the person responsible for this improvement.
Whilst aboard the cruise ship Finland in late October 1925, travelling with three friends, all of whom were auction bridge enthusiasts; he tested an idea for making the auction bridge version of the game more interesting.
Vanderbilt decided to make it more challenging by requiring a partnership to actually bid to the game or slam level in order to receive a bonus. Since this refinement made slam risky to attempt, he also increased the slam bonuses.
Vanderbilt devised the first unified system of bidding, and he was solely responsible for the artificial 1C bid to show a strong hand, the negative 1D response, the strong (16-18 HCP) notrump on balanced hands only and the weak two bid opening.
He authored several bridge books and was a member of the Laws Committee of the Whist Club of New York that made the American laws of contract bridge (1927, 1931) and the first international code (1932).