Alaska is about 8 times bigger than South Dakota.

South Dakota is approximately 196,540 sq km, while Alaska is approximately 1,481,348 sq km, making Alaska 654% larger than South Dakota. Meanwhile, the population of South Dakota is ~814,180 people (103,949 fewer people live in Alaska).
Tip: This to-scale comparison of South Dakota vs. Alaska uses the Mercator projection, which distorts the size of regions near the poles.