District of Columbia is about 1.7 times bigger than Montserrat.

Montserrat is approximately 102 sq km, while District of Columbia is approximately 177 sq km, making District of Columbia 74% larger than Montserrat. Meanwhile, the population of Montserrat is ~5,414 people (596,309 more people live in District of Columbia).
Tip: This to-scale comparison of Montserrat vs. District of Columbia uses the Mercator projection, which distorts the size of regions near the poles.