The first game was believed to be a modified version of rugby and football, played in 1869 between Rutgers and Princeton. Walter Camp was the first to personally write the rules during the Massasoit convention in 1876. Due to the game's growing popularity, many local athletic clubs adopted it and began playing it competitively against each other. From 1892 to 1895, clubs began paying and contracting players, which led to the creation of the first professional team in 1896. Once teams began to form, a professional soccer league was established along with the first World Series in 1902. In 1903, while many college teams played the sport, Harvard became the first university to build a stadium designed for football. After being very popular in the Pennsylvania area, popularity shifted to Ohio, which had seven professional teams at the time. These seven teams formed their own league, which had created its own universal rules, and played for an Ohio League championship. Organizations faced problems with the salary difference and constant changing of teams for the most popular players. By 1920, the teams came to a conclusion about the recurring problems that were occurring. This led to the inception of the APFA, American Professional Football Conference, and by 1922 football had become a more established game with 18 active football teams, mostly in the Midwestern states. This year the name was also changed to the name everyone knows today, the National Football League or NFL. The NFL began to attract more national attention as more star college players began signing contracts with NFL organizations. In 1925, approximately 36,000 fans attended the Chicago Bears' game against the Chicago Cardinals. The popularity of football began to take off and arrived in the same year