Eastern Idaho State Fair September 5 - 12, 2015 The Eastern Idaho State Fair is a 16 County Fair District. Over 220,000 people visit the annual event, making it Eastern Idaho’s longest running and largest annual community event. The mission of the EISF is to provide wholesome, affordable family education and entertainment in a clean and safe agricultural environment. It’s never too early to get excited for next year’s fair which will be held September 5 - 12, 2015!