The UK's first ten National Parks were all established in the 1950s, starting with the Peak District in 1951 and continuing up to the Brecon Beacons in 1957. There was then a gap to 1989, when the Broads were designated, and four more were established in the first decade of the 21st century – making a total (to date) of fifteen.
The Yorkshire Dales was the UK's sixth (or seventh) National Park. The reason for my prevarication is that the official Government page archived on the Wayback Machine lists it sixth, giving an establishment date of 16 November 1954, followed by Exmoor with a date of 19 October 1954!
© Macclesfield Quiz League 2019