Garrison is a city in McLean County, North Dakota, United States. The population was 1,462 at the 2020 census. Garrison was laid out in 19…Garrison is a city in McLean County, North Dakota, United States. The population was 1,462 at the 2020 census. Garrison was laid out in 1905 when the Soo Line Railroad was extended to that point. The town took its name from Garrison Creek. A post office has been in operation at Garrison since 1903.