Jim Bradshaw: Who put 'old' and 'Spanish' in Old Spanish Trail?

A cadre of cultural leaders from across south Louisiana and beyond will gather at the Rayne Civic Center on Sept. 25 to explore the origins and influence of the roadway called the Old Spanish Trail that linked our Main Streets before an Interstate isolated most of them.
The notice of the annual meeting caused me to wonder about several questions:
How did it get its name? How old is it? And how Spanish is it? It seems nobody knows for sure.
Highways had names before they had numbers, and the Old Spanish Trail was one of the best-known of them. It followed the Gulf Coast from St. Augustine, Florida, and came into Louisiana at Slidell.
From there it continued through New Orleans to Morgan City, then up the Teche to Berwick, Patterson, Centerville, Franklin, Baldwin, Jeanerette and New Iberia.
It began a westerly trek at Broussard, going through Lafayette, Scott, Rayne, Crowley, Mermentau, Jennings, Welsh, Iowa, Lake Charles, Sulphur and Vinton. After it crossed into Texas at Orange it stretched across the sunbaked Southwest.
The idea for the 3,000-mile route ending in San Diego, and for its name, stemmed from a national Good Roads Movement that caught the attention of the Rotary Club in Mobile in 1915.
Its members were afraid that their town would be overlooked in the growing push for better highways.
Four hundred people from Alabama and neighboring states attended a conference called by the club. They formed the Old Spanish Trail Association to lobby for a road to “afford tourists the ability to see Florida towns, come through Mobile, and go west along the Mississippi coast through New Orleans and to California.”
The association promoted the route as the one used by early Spanish explorers, but as Karen LeBlanc pointed out in a Louisiana Public Broadcasting documentary, “The highway’s lore is more romance than record. … It’s a great name … [but] there was never one continuous conquistador road running unbroken from Florida to California.
"What the highway did follow, at least here in Louisiana, was the high ground — the ridges and natural levees that Indigenous people, drovers, and traders had used for generations to stay out of the swamp.”
LeBlanc will headline the Rayne conference that will deal mostly with finding ways to showcase OST communities and bring visitors to them. The question about the name is not on the agenda, but I am apparently not the only one to wonder about it.
I have seen accounts of “the old trail” used to link New Orleans and Sante Fe after Louisiana was given to Spain and have also read about drovers following “an old Spanish trail” when they were taking herds from southeast Texas and southwest Louisiana to market in New Orleans, but both of those were generic references, not about a specific route.
I suspect that a trail of some sort or, more likely, a series of interconnected trails, existed at least from the time of Spanish Louisiana, and probably earlier, but that it was called something other than the Old Spanish Trail, if it had a name at all.
Eddie Palmer, who has helped organize annual OST Days in Rayne since 2016, searched the Old Spanish Trail Association files archived at St. Mary’s University in San Antonio and found a document in which the association’s managing director said he did not know exactly how the name came about. 
Palmer found other documents suggesting that representatives of highway associations in western and central Florida argued for the name at the 1915 conference because they were already using it for what was to become Highway 90.
He guesses that “the Florida highway associations probably used that name due to the numerous Spanish missions that once stood in their districts around the northern rim of Florida.”
LeBlanc suggests the same thing, noting that the archives “do not give the exact reason,” but Old Spanish Trail “was possibly selected …  because of the … numerous Spanish Missions … in northern Florida and in Texas, New Mexico, Arizona, and California.”
However it got its name, communities in south Louisiana have been happy to use it to encourage visitors to come see us. For example, a coalition of Louisiana towns several years ago touted the OST as a scenic byway “spanning prairies and swamps, Creoles and Cajuns, alligators and crawfish, sugarcane and peppers, Zydeco and Cajun, and the annual blessing of the shrimp fleets.”
The old road still spans those things and  more, and that’s part of what the Rayne conference wants to point out.
You can contact Eddie Palmer at epalme@bellsouth.net for conference details, or me if you have a clue about who named the road and when.
You can contact Jim Bradshaw at jimbradshaw4321@gmail.com or P.O. Box 1121, Washington LA 70589.