Cowboy boots may have changed the least over time. Such embellishments as high heels and decorated uppers appeared early as cowboys tried to set themselves apart, Reeves said.
"Even in the 1870s, they would try to show that 'I'm a Texan, I'm a cowboy, I don't walk behind a plow,'" he said.
It wasn't until the 1920s and 30s, years after the cattle drives that made the cowboy an American hero, that the style we recognize today as Western wear began to emerge, Reeves and Weil said.
That had as much to do with Hollywood and the music business as it did with working cowboys.
"Western fashion as we know it really came into its own with the movies, the Western movie," Weil said. Before the 1920s, "Western fashion as we know it did not exist."
The look hit its zenith in the 1940s with the fancy outfits of Roy Rogers and Gene Autry, the singing cowboys and movie stars, Reeves said. "The Lone Ranger" and "Hopalong Cassidy" TV Westerns carried the look in the 1950s.
Reeves once saw an original Lone Ranger costume, including stretchy blue tights. "It was, ew-w-w, kind of scary. You looked at the suit and it was kind of like dance class," he said.
But the Lone Ranger's hat, boots and gun belt were enough to convince audiences that he was a cowboy.
"Even though the rest of it had more to do with leotards than what cowboys wore, we said, 'Yeah, that's a cowboy.' We made that cognitive leap," Reeves said.
Rodeo performers in the early 1900s had an underrated influence on the Western look, Reeves said. They started wearing bigger hats and brighter colors to get noticed, and teenagers in the audience began to imitate the style when they dressed up for a dance, if not when they went to work in the saddle.