Wellsville, Ohio is a village in Columbiana County, Ohio, United States, along the Ohio River. It is in Yellow Creek Township, Columbiana County, Ohio. Wellsville was founded about 1795 and grew in the 19th and early 20th centuries. In 1838 the population was 759. By 1900 the U.S. Census showed the population at 6,146. In 1920 the city peaked at 8,849 according to the Census. Since then, each census shows the population declining.