The original was formed in 1967 when the competing United Soccer Association and the National Professional Soccer League decided to join forces. For the next 12 seasons, it was the top-level league for outdoor soccer in the U.S. and Canada. In the late '70s and early '80s, it also played an indoor schedule to compete with the suddenly popular . The NASL grew slightly in popularity in the 1970s and expanded to a high of 24 teams for three seasons starting in 1978. However, not all cities embraced the league and it soon began to shrink, folding after the 1984 season and leaving the U.S. without a top-level, pro soccer league for the next 12 years.