Historical clue formulations

• Southernmost country in Central America — 2026-06-01
• Canal locale — 2023-02-14
• First airline to complete a round-the-world flight — 2021-08-26
• Country on an isthmus — 2019-12-31
• Summer hat — 2019-08-07
• Summer hat — 2018-12-23
• Article of apparel not originating where its name would suggest — 2018-04-07
• Isthmus land — 2017-05-23
• With 6-Down, bit of summer wear — 2015-10-02
• Article of apparel that's not made where you might think — 2012-08-19
• Southernmost country in Central America — 2010-08-24
• Central American canal locale — 2009-06-22
• Summer topper — 2007-11-04
• Hat made of jipijapa — 2006-11-08
• Boater alternative — 2006-04-29
• Kind of hat — 2002-09-18
• Where to spend a balboa — 2001-01-26
• Kind of hat — 2000-11-20
• Canal site — 1999-11-22
• Lightweight hat — 1998-06-24
• Summer hat — 1998-05-23
• Hat made from jipijapa — 1996-09-05
• Summer hat — 1994-05-29