District of Columbia is about 3.8 times bigger than Pitcairn Islands.

Pitcairn Islands is approximately 47 sq km, while District of Columbia is approximately 177 sq km, making District of Columbia 277% larger than Pitcairn Islands. Meanwhile, the population of Pitcairn Islands is ~50 people (601,673 more people live in District of Columbia).
Tip: This to-scale comparison of Pitcairn Islands vs. District of Columbia uses the Mercator projection, which distorts the size of regions near the poles.