Portland is about 2.6 times smaller than Dayton.

Dayton is approximately 145 sq km, while Portland (map shows its 17 named neighbourhoods; the area covers the whole city) is approximately 56 sq km, making Portland 38.59% the size of Dayton.
Tip: This to-scale comparison of Dayton vs. Portland uses the Mercator projection, which distorts the size of regions near the poles.
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