Oswego is a city in Oswego County, New York, United States. The population was 16,921 at the 2020 census. Oswego is located on La…Oswego is a city in Oswego County, New York, United States. The population was 16,921 at the 2020 census. Oswego is located on Lake Ontario in Upstate New York, about 35 miles northwest of Syracuse. It promotes itself as "The Port City of Central New York." It is the county seat of Oswego County.