South Dakota is around the same size as Idaho.

Idaho is approximately 214,314 sq km, while South Dakota is approximately 196,540 sq km, making South Dakota 91.71% the size of Idaho. Meanwhile, the population of Idaho is ~2.0 million people (1.1 million fewer people live in South Dakota).
Tip: This to-scale comparison of Idaho vs. South Dakota uses the Mercator projection, which distorts the size of regions near the poles.
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