Dominica is about 4.2 times bigger than District of Columbia.

District of Columbia is approximately 177 sq km, while Dominica is approximately 751 sq km, making Dominica 324% larger than District of Columbia. Meanwhile, the population of District of Columbia is ~601,723 people (527,094 fewer people live in Dominica).
Tip: This to-scale comparison of District of Columbia vs. Dominica uses the Mercator projection, which distorts the size of regions near the poles.