Historical clue formulations

• Water containers — 2026-09-18
• Barriers to entry, in a way — 2026-05-29
• Hydroelectric projects — 2025-01-26
• Stops up — 2024-06-18
• River blockers — 2023-12-11
• Holds back, in a way — 2022-07-30
• Blocks — 2021-08-13
• Stops up — 2020-09-06
• Blocks off — 2018-06-01
• Civil engineering projects — 2016-11-11
• Creators of artificial lakes — 2016-07-20
• Challenges for salmon — 2015-02-11
• Beaver projects — 2014-06-10
• Lake creators — 2013-08-06
• Beavers build them — 2012-12-25
• Blockades, of a sort — 2012-07-19
• Blocks (up) — 2012-04-08
• Beaver constructions — 2011-12-26
• Projects for beavers — 2011-10-10
• Blocks — 2011-07-10
• Beaver constructions — 2011-01-17
• Reservoir producers — 2010-03-17
• Hoover and others — 2005-05-22
• Power sources — 2005-04-07
• Stops up — 2004-12-26
• Blocks — 2001-12-09
• Hungry Horse and Mossyrock — 2001-11-22
• Farm mothers — 2000-07-12
• Stops up — 2000-04-11
• Stops up — 1998-05-03
• Beavers' constructions — 1997-06-02
• Stops up — 1997-05-03
• Creek constrictors — 1995-12-15
• Hoover and Roosevelt, e.g. — 1995-08-17
• Beavers' constructions — 1995-06-12
• Beaver projects — 1994-10-04