King County Fair in Enumclaw | Slideshow The four-day King County Fair celebrated its 150th birthdayAug. 3-5 under sunny skies. By Kevin Hanson • August 10, 2012 8:05 pm The four-day King County Fair celebrated its 150th birthday last week under sunny skies. The four-day King County Fair celebrated its 150th birthdayAug. 3-5 under sunny skies.