District of Columbia is about 2,130 times smaller than Montana.

Montana is approximately 376,979 sq km, while District of Columbia is approximately 177 sq km, making District of Columbia 0.05% the size of Montana. Meanwhile, the population of Montana is ~989,415 people (387,692 fewer people live in District of Columbia).
Tip: This to-scale comparison of Montana vs. District of Columbia uses the Mercator projection, which distorts the size of regions near the poles.