From U.S. Census Bureau data for 2025.
Montgomery County had an estimated 539,598 residents on July 1, 2025, according to the Census Bureau, up 2,668 from a year earlier.
The county’s highest estimate in these records is 608,413, in 1970.
See the full history and data on Dayton by the Numbers →
Each year’s release revises earlier estimates.
Source: U.S. Census Bureau, Population Estimates Program (through FRED, Federal Reserve Bank of St. Louis). How the figures are built: methodology.
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