Historical clue formulations

• Wash. neighbor — 2021-01-10
• Where the John Day R. flows — 2012-06-23
• State north of Calif. — 2012-02-13
• Wash. neighbor — 2008-08-03
• Salem's state: Abbr. — 2008-05-20
• Neighbor of Wash. — 2007-06-27
• Wash. neighbor — 2006-02-27
• It touches the Pacific O. — 2005-04-17
• Wash. neighbor — 2003-11-10
• Its state tree is the Douglas fir: Abbr. — 2002-06-07
• Calif. neighbor — 2001-10-01
• Neighbor of Calif. — 2001-03-27
• 33rd state: Abbr. — 2000-02-26
• Portland's state: Abbr. — 1996-10-07