What is the flattest state in the United States? And the most mountainous?

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Dear Tom,
What is the flattest state in the United States? And the most mountainous?
— Thomas Majora,
Chicago
Dear Thomas,
Most people will guess that Kansas is the flattest state among the 50, but it’s not. The flattest is Florida, and Kansas isn’t even among the five flattest. In order of flatness: Florida, Illinois, North Dakota, Louisiana, Minnesota, Delaware, Kansas. So, Kansas is seventh-flattest, and Illinois — yes, Illinois — ranks second-flattest.
Ranking states according to mountainous terrain is more difficult. States with the highest mountains — Alaska, California and Colorado — also contain extensive plains and relatively flat valleys. It turns out that West Virginia is the nation’s most mountainous state, though its highest peak, Spruce Mountain, is only about 4,864 feet in height.