James Naismith, a Canadian physical education teacher, invented basketball in Springfield, Massachusetts, in 1891 as a less injury-prone sport than football. During the winter, Naismith, a 31-year-old graduate student, invented indoor sports to keep participants indoors. The game gained popularity rather fast when it was invented, initially in America and thereafter in other countries during the 20th century. The professional game of basketball emerged when basketball gained traction in American universities. By the end of the 20th century, the American National Basketball Association (NBA), founded in 1946, had grown to be a multibillion dollar industry and basketball had become ingrained in American society.