District of Columbia is about 1.3 times smaller than Martha's Vineyard.

Martha's Vineyard is approximately 227 km² (87 sq mi), while District of Columbia is approximately 177 sq km, making District of Columbia 78.12% the size of Martha's Vineyard.
Tip: This to-scale comparison of Martha's Vineyard vs. District of Columbia uses the Mercator projection, which distorts the size of regions near the poles.
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