Historical clue formulations

• Major highway through the southern U.S. — 2024-11-21
• Main lower artery, informally — 2019-10-18
• Major Calif.-to-Fla. route — 2018-02-12
• Calif.-to-Fla. route — 2018-01-23
• Cross-country route, informally — 2017-09-28
• Major thoroughfare through Houston, informally — 2017-07-13
• Southern hwy. — 2014-05-22
• Christopher Columbus Transcontinental Hwy. — 2014-01-24
• Major Fla.-to-Calif. route — 2013-08-12
• Calif.-to-Fla. hwy. — 2013-03-03
• Major Calif.-to-Fla. route — 2012-10-15
• Major artery through San Antonio — 2012-01-15
• L.A.-to-Jacksonville rte. — 2011-01-20
• Eight-state coast-to-coast rte. — 2008-06-07
• Major Calif.-to-Fla. route — 2007-05-15
• Tucson-to-New Orleans route — 2007-03-13
• Highway damaged by hurricane Katrina — 2006-11-19
• Coast-to-coast hwy. — 2006-03-16
• Calif.-Fla. route — 2005-10-13
• L.A.-to-Jacksonville route — 2004-06-04
• Major Calif.-to-Fla. route — 2000-11-21