State size comparison

compared to

South Dakota is about 1.4 times bigger than Illinois.

Illinois is approximately 143,961 sq km, while South Dakota is approximately 196,540 sq km, making South Dakota 37% larger than Illinois. Meanwhile, the population of Illinois is ~12.8 million people (12.0 million fewer people live in South Dakota).
Tip: This to-scale comparison of Illinois vs. South Dakota uses the Mercator projection, which distorts the size of regions near the poles.
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Compare further: South Dakota vs. Illinois

Flip Comparison · See true size
See South Dakota on top of Illinois
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Quality of Life Comparison · 14 statistics
Be 100.0% more likely to be unemployed in Illinois
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Cost of Living Comparison · 7 categories - 2026 data
Illinois is 35.6% more expensive than South Dakota
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