It's not just a popular idiom. The state was proven to be flatter when scientists bought a pancake from an IHOP and tested the topography against the flatness of the state. They measured "perfect flatness" on a scale of 1 with the IHOP pancake testing as 0.957 and Kansas scoring a 0.997.
A ball of twine in Cawker City measures over 38' in circumference and weighs more than 16,750 pounds and is still growing.
South of Ashland the Rock Island Bridge is the longest railroad bridge of its kind. It measures 1,200 feet long and is 100 feet above the Cimarron River.
At one time it was against the law to serve ice cream on cherry pie in Kansas.