The hyungs (as they where originally refered to) where created in the following order:
Pyung An - these are the hyungs of the Japanese / Okinawan Karate-do that returned to Korea where they where practices by the students of Tang Soo Do (Korean transliteration for the word Karate)
Chang Hon Hyungs (ITF-including Chon Gi) Introduced beginning in 1955
Pal-Gwe Hyungs - Created around or just before the inception of the WTF (approx 71'-73')
Tae-Geuk Poomse - Created to modernize the WTF curricullum (as the Pal-Gwe where much like Kata of Karate-do). I believe these where introduced in the 80's but Im not the WTF-Kukkiwon expert on this site)