A city of Campbell county, Kentucky, U.S.A., on the S. bank of the Ohio river, opposite Cincinnati, and adjoining Bellevue and Newport, Ky. Pop. (1890) 4264; (1900) 6104, of whom 655 were foreign-born and 63 were negroes. It is served by the Chesapeake & Ohio railway at Newport, of which it is a suburb, largely residential. It has manufactories of watch-cases and pianos, and whisky distilleries. In the city is the Speers Memorial hospital. Dayton was settled and incorporated in 1849.