sidneySidney is a town in Delaware County, New York, United States. The population was 5,536 at the 2020 census. [3] [4] The town is at the northwestern corner of the county and containsSidney is a city in and the county seat of Cheyenne County, Nebraska, United States. [5] The city is nine miles (14 km) north of the Colorado state . The population was 6,410 at the 2020