Saint Lucia is about 3.5 times bigger than District of Columbia.

District of Columbia is approximately 177 sq km, while Saint Lucia is approximately 616 sq km, making Saint Lucia 248% larger than District of Columbia. Meanwhile, the population of District of Columbia is ~601,723 people (434,601 fewer people live in Saint Lucia).
Tip: This to-scale comparison of District of Columbia vs. Saint Lucia uses the Mercator projection, which distorts the size of regions near the poles.