Grafton is a city and the county seat of Walsh County, North Dakota, United States. The population was 4,170 at the 2020 census. makin…Grafton is a city and the county seat of Walsh County, North Dakota, United States. The population was 4,170 at the 2020 census. making Grafton the 17th largest city in North Dakota. Grafton was founded in 1881.