Simplify the following text for a Grade 11 native English-speaking person.
Original: The West Division of the National Hockey League existed from 1967 , when the NHL was made up of a single division , until 1974 when the league changed its format into two conferences of two divisions each .
Simplified: The West Division of the National Hockey League existed from 1967 until 1974 when the league realigned into two conferences of two divisions each .