Historical clue formulations

• 406, for the entire state of Montana — 2025-05-05
• 918 or 539, on the Cherokee Nation — 2025-02-18
• Numerical trio — 2020-07-16
• One of seven for New York City — 2018-12-19
• Prefix with triple digits — 2010-07-08
• Prefix in parentheses — 2009-01-09
• Parenthetical information — 2007-03-23
• Parenthetical information — 2005-05-08
• Locale identifier — 2004-03-12
• Opening number — 2002-03-01
• 201, e.g. — 2002-01-16
• Regional figure — 2000-07-01
• Parenthetical figure — 2000-01-23
• Information information — 1999-10-29
• Three before seven — 1998-11-05
• Customer file entry — 1998-10-24
• Three-digit number — 1998-05-01
• Three before seven — 1998-04-17
• Important prefix — 1997-07-12
• Prefix, of sorts — 1996-02-18
• 409, e.g. — 1996-01-20
• Hawaii's is 808 — 1995-01-19
• 201 or 202, e.g. — 1994-05-22
• Number after 1? — 1994-02-04