Stumbled across a fascinating YouTube channel about national parks (worldwide), and #TodayILearned that the US National Park Service brochure employs a design system called the #Unigrid, designed by none other than #MassimoVignelli, who said it was one of the most important projects he ever worked on -

https://www.nps.gov/subjects/hfc/a-brief-history-of-the-unigrid.htm

For some great throwback design, scroll down to 1965 on this list of old NPS brochure designs.

https://www.nps.gov/parkhistory/online_books/brochures/year-1960.htm