sidneySidney is a city in Shelby County, Ohio, United States, and its county seat. [4] The population was 20,421 at the 2020 census.It is approximately 36 miles (58 km) north of Dayton and 100 milesSidney Spit is accessible all year by boat or kayak. A passenger ferry runs from the wharf on Beacon Street in Sidney from mid-May until Labor Day weekend in September. Related