Tioga is a city in Williams County, North Dakota, United States. The population was 2,202 at the 2020 census. Tioga was founded in 190…Tioga is a city in Williams County, North Dakota, United States. The population was 2,202 at the 2020 census. Tioga was founded in 1902 and named by settlers from Tioga, New York. The population of the city increased dramatically in the 1950s following the discovery of oil nearby in the Williston Basin.