Northern Mariana Islands is about 2.6 times bigger than District of Columbia.

District of Columbia is approximately 177 sq km, while Northern Mariana Islands is approximately 464 sq km, making Northern Mariana Islands 162% larger than District of Columbia. Meanwhile, the population of District of Columbia is ~601,723 people (550,248 fewer people live in Northern Mariana Islands).
Tip: This to-scale comparison of District of Columbia vs. Northern Mariana Islands uses the Mercator projection, which distorts the size of regions near the poles.