McHenry is a city in Foster County, North Dakota, United States. The population was 64 at the 2020 census. McHenry was founded in 189…McHenry is a city in Foster County, North Dakota, United States. The population was 64 at the 2020 census. McHenry was founded in 1899. According to the United States Census Bureau, the city has a total area of 0.26 square miles, all land.