Historical clue formulations

• When repeated, a Northwest city — 2018-01-05
• When doubled, a Washington city, county or river — 2016-01-24
• When repeated, Columbia feeder — 2009-08-22
• When repeated, a city in Washington — 2005-02-08
• Doubled, home of Whitman College — 2004-06-24
• When doubled, a Washington city — 2001-04-17
• When repeated, a Washington city — 1999-03-22
• When doubled, a Washington city — 1999-01-03
• When repeated, a Western city — 1998-07-16
• When repeated, a Washington city — 1998-05-05
• *Home of Whitman College — 1997-05-01
• When repeated, an Evergreen State city — 1996-02-20
• Half of a Western city name — 1994-02-22