Cook Islands is about 1.3 times bigger than District of Columbia.

District of Columbia is approximately 177 sq km, while Cook Islands is approximately 236 sq km, making Cook Islands 33% larger than District of Columbia. Meanwhile, the population of District of Columbia is ~601,723 people (593,595 fewer people live in Cook Islands).
Tip: This to-scale comparison of District of Columbia vs. Cook Islands uses the Mercator projection, which distorts the size of regions near the poles.