But like the neighboring states, bluegrass and country remain stubbornly independent of each other, maintaining distinctive personalities despite morphing in plenty of other directions.
Country music has ventured into straight-ahead pop. The country rock movement of the late 1960s and early '70s still lingers. Southern rock has returned to its country roots. There's alt.-country and progressive country and the big sound of arena country.
Similarly, name the shade, and bluegrass has likely colored it, from psychograss to jazzgrass to spacegrass.
Yet countrygrass, or if you prefer, bluecountry, for whatever reason, has never seemed to take root. There are exceptions, of course such as Alison Krauss, Patty Loveless and Vince Gill, who have managed to bridge the two with a measure of commercial success.
But the chilly waters still separating two genres may be warming just a bit with the latest release by Mountain Heart, "Open Space."
The bluegrass group has steadily grown a legion of fans during its seven-year, five-album run. Yet, one Mountain Heart fan in particular could very well help the group find a home on the country charts, while remaining a staple of bluegrass.
Country music producer Mark Bright, who helped shape Rascal Flatts' distinctive high-harmony, acoustic-based sound, signed on last year to produce "Open Space."
Bright also produced country superstar Sara Evans' 2005 release "Real Fine Place," helping keep her atop the charts as well as "American Idol" winner Carrie Underwood's country music smash debut, "Some Hearts."
So what's a Nashville über-producer and industry power broker doing producing a bluegrass group that admittedly has had a difficult time mustering sales of 10,000 units for any of its albums?
After all, there's no guarantee Mountain Heart can spin gold on Ricky Skaggs' small, independent Skaggs Family Records label merely because Bright is producing it.
Simply put, Bright is among Mountain Heart's biggest fans. It came as a big surprise to Jim Van Cleve, Mountain Heart's co-founder and fiddle player.
"The average listener won't care who Mark Bright is," says Van Cleve, who along with guitarist-singer-songwriter Steve Gulley and banjoist Barry Abernathy helped found Mountain Heart when he was barely 20 years old.
"And it was a simple twist of fate that we got him to produce our record."
Van Cleve says he was across the street from Evans, who was doing some demo records with Bright for "Real Fine Place." Evans' manager knew of Mountain Heart and urged Van Cleve to meet Bright.
"Mark is a big bluegrass fan, so I walked over there," Van Cleve recalls. "I introduced myself, and he said, 'I know exactly who you are! You're Mountain Heart!' My jaw about hit the floor. I was holding a copy of (Mountain Heart's album) 'Force of Nature' and gave it to him when he said, 'I already have one; I bought it."
"So Sara is doing a demo song, and Mark is reading our liner notes. I'm standing in the studio watching this, and I can't believe it."
Van Cleve says the band had toyed with the idea of getting someone such as Krauss to produce their next record, but it never materialized. So he seized the opportunity that presented itself.
"I asked him if he would be interested in producing us; I thought he would say maybe somewhere down the road we could work together," Van Cleve says. "Then Mark said, 'I would literally jump at the chance to work with you.' I couldn't leave that alone. I called my manager - 'Let me tell you what just happened,' I said. And we were off."
Bright told him, "Here's how we'll start," and it grew from there. Mountain Heart members received a CD a week from Bright, all containing potential material for the new album.
"They were all good songs," Van Cleve says. "It was all killer material. We could've cut two or three records. But through the process, we narrowed it down. We were taking songs that were top demos."
Not only that, they worked in Nashville's best studios with the brightest technical people in town, Van Cleve says.
"The engineers (Derek Bason and David Hall) are the best in Nashville; these guys are at the top of their game," he says. "You have to understand, bluegrass bands don't get that kind of chance. The material, our own growth as a band, us understanding we're in the best studios in the world - the combination is definitely produced our strongest album yet."
Van Cleve admits there could be a backlash, that some in bluegrass won't see it as a bluegrass album, and some in country won't see it as a country album.
"I'm concerned about mixed reviews," he says. "We're not wearing two hats - one bluegrass and one country. We're wearing one hat that encompasses both; plus, we're a jam band."