Buffalo is a city in Cass County, North Dakota, United States. The population was 195 at the 2020 census. Buffalo was founded in 1878…Buffalo is a city in Cass County, North Dakota, United States. The population was 195 at the 2020 census. Buffalo was founded in 1878. The first settlement at Buffalo was made in 1878. A post office called Buffalo has been in operation since 1883. The city took its name from Buffalo, New York.