Cayman Islands is about 1.5 times bigger than District of Columbia.

District of Columbia is approximately 177 sq km, while Cayman Islands is approximately 264 sq km, making Cayman Islands 49% larger than District of Columbia. Meanwhile, the population of District of Columbia is ~601,723 people (537,414 fewer people live in Cayman Islands).
Tip: This to-scale comparison of District of Columbia vs. Cayman Islands uses the Mercator projection, which distorts the size of regions near the poles.