Complex sentence: Many of these were markets that had been served by the defunct World Hockey Association or abandoned by the NHL, but the IHL also placed teams in markets that already had NHL teams, such as Chicago, Detroit, and Long Beach (near Los Angeles).
Split into simpler sentences: Many of these were markets were served by the defunct World Hockey Association or were abandoned by the NHL. The IHL also entered markets that already had NHL teams, such as Chicago, Detroit, and Long Beach (near Los Angeles).