Historical clue formulations

• Numbers that come after 1 — 2022-06-24
• Some demographic data — 2019-08-10
• Regional IDs — 2016-09-10
• Long-distance callers' necessities — 2014-09-08
• 409 and 410, but not 411 — 2014-07-11
• Prefixes featured on some maps — 2013-09-27
• New York City has six — 2012-09-07
• 307 for Wyoming and 907 for Alaska — 2009-05-06
• New York City has five — 2002-03-23
• 727 and others — 2001-03-03
• Many new numbers these days — 2000-12-03
• They're often found in parentheses — 1999-08-14
• Numbers usually in parentheses — 1998-08-10
• Long-distance needs — 1995-09-15
• Numbers in parentheses — 1994-07-27