Senegal is around the same size as South Dakota.

South Dakota is approximately 196,540 sq km, while Senegal is approximately 196,722 sq km, making Senegal 0% larger than South Dakota. Meanwhile, the population of South Dakota is ~814,180 people (17.1 million more people live in Senegal).
Tip: This to-scale comparison of South Dakota vs. Senegal uses the Mercator projection, which distorts the size of regions near the poles.