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

District of Columbia is approximately 177 sq km, while Martha's Vineyard is approximately 227 km² (87 sq mi), making Martha's Vineyard 28% larger than District of Columbia.
Tip: This to-scale comparison of District of Columbia vs. Martha's Vineyard uses the Mercator projection, which distorts the size of regions near the poles.
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