South Dakota is around the same size as Uruguay.

Uruguay is approximately 176,215 sq km, while South Dakota is approximately 196,540 sq km, making South Dakota 12% larger than Uruguay. Meanwhile, the population of Uruguay is ~3.4 million people (2.6 million fewer people live in South Dakota).
Tip: This to-scale comparison of Uruguay vs. South Dakota uses the Mercator projection, which distorts the size of regions near the poles.