Historical clue formulations

• North Dakota city — 2015-10-28
• North Dakota city with a nearby Air Force base — 2015-08-11
• North Dakota city — 2005-12-12
• North Dakota city with an air force base — 2005-07-17
• Amtrak station west of Grand Forks — 2004-07-30
• North Dakota city — 2003-12-06
• Seat of Ward County, N.D. — 2003-11-21
• Seat of Ward County, N.D. — 2002-05-16
• North Dakota city — 1998-08-30