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is a city in Montgomery and Miami Counties in the U.S. state of Ohio. The population was 13,347 at the 2000 census. It is part of the Dayton Metropolitan Statistical Area. In 1998, Clayton merged with the remainder of Montgomery County's Randolph Township.
According to the United States Census Bureau, the city has a total area of 18.6 square miles (48.1 km²), of which, 18.4 square miles (47.8 km²) of it is land and 0.1 square miles (0.3 km²) of it (0.59%) is water.