History
In 1967, the North American Soccer League (NASL) announced that it would begin play the following year. Almost immediately afterward, a group of investors formed the National Professional Soccer League (NPSL), to begin play in 1967.
Among the NPSL's backers were Art Rooney, owner of the NFL's Pittsburgh Steelers, and Jerry Hoffberger, owner of baseball's Baltimore Orioles. It had 10 teams: the Atlanta Chiefs, Baltimore Bays, California Clippers, Chicago Spurs, Los Angles Toros, New York Generals, Philadelphia Spartans, Pittsburgh Phantoms, St. Louis Stars, and Toronto Falcons.
The NASL responded quickly by changing its name to the United Soccer Association (USA), to avoid confusion with the NPSL, and starting play a year ahead of schedule. The only way to do that, though, was by importing entire foreign teams.
Because the NPSL was not sanctioned by soccer's national and international governing bodies, as the USA was, its teams had problems finding players, since they faced possible suspension for playing in the league.
However, the teams were finally stocked and the season played. But poor attendance forced the NPSL to merge with the USA as the North American Soccer League in 1968.
NOTE: The second Major Indoor Soccer League was also once known as the National Professional League.