Complex sentence: In 1976, the Government of Quebec acquired part of the mountain and established a park in 1985 that since 1999, is managed by the Société des établissements de plein air du Québec (SÉPAQ).
Split into simpler sentences: In 1976, the Government of Quebec acquired part of the mountain. It established a park in 1985 that, since 1999, is managed by the Société des établissements de plein air du Québec (SÉPAQ).