 The league operated at the Class A level for one year (1963), before changing to Rookie league in 1964, when there were only four teams in the league; the Idaho Falls Angels, Magic Valley Cowboys, Pocatello Chiefs, and Treasure Valley Cubs.By 1978, the league had again grown to eight teams — Billings and Idaho Falls along with the Butte Copper Kings, Calgary Cardinals, Great Falls Giants, Helena Phillies, Lethbridge Dodgers, and Medicine Hat Blue Jays.With the exception of 1986 (when there were six teams), there have been eight teams in the league since then, and it is not likely to change without further expansion or contraction within Major League Baseball.