Shelley is a city in Bingham County, Idaho, United States. The population was 4,409 at the 2010 census. The mascot for the city's high school is a russet-burbank potato that wears a crown, robe and scepter.Since 1927 Shelley has been home to the "Idaho Annual Spud Day", which is celebrated on the 3rd Saturday of September. It typically features a parade, live bands, a Spud Tug, a spud-picking Contest, and free baked potatoes.