"It was a really good job," says the Kentucky-born singer, songwriter and guitarist, who has emerged as an overnight sensation in the country music world despite holding to a musical policy that refuses to go with what's new and trendy, staying true to the honky-tonky country and bluegrass styles he grew up with. "I really enjoyed working on the railroad for the first four years but the minute they put me on the management team, in 2010, all the fun seemed to disappear."
So a decision was reached. Simpson and his wife moved to Nashville without any kind of plan. He just knew that Nashville was where the music industry was and if he had any chance of making music his life, as he'd hoped for from the moment he'd first picked up a guitar, then this was where that could happen.
Four years on, with two albums released in quick succession over the past few months, things are looking good.
"They say it's happened overnight," he says. "But it doesn't really feel that way. There was a lot of groundwork beforehand and there's a lot of frustration when you're just starting out. For instance, I sent out copies of the first album myself and because it wasn't on a major label, it pretty much got ignored in the States. Then a publicist handles the second one, obviously knows how to reach the right targets, and suddenly the people who passed over the first album are talking about it like they knew about it all along."
Those first two albums, High Mountain Top and Metamodern Sounds in Country Music, and possibly their next five successors, represent a stockpile of songs that Simpson wrote while waiting for his chance to make his mark in music.
Back home in Versailles, Kentucky, he'd grown up surrounded by music. Both his grandparents and an uncle played guitar. His paternal grandfather, who has a song, Hero, dedicated to him on High Mountain Top, made sure that the youngster heard all the bluegrass and country records that mattered and was the main inspiration for Simpson becoming proficient as a guitarist by the time he was a teenager. Various musical obsessions took over in high school - a cover version of synth-pop band When in Rome's The Promise on his second album hints at one of these - and Simpson played in his first band, gaining valuable early experience of "playing to large numbers of inebriated people" while still underage thanks to an understanding bar owner.
"I'd love to say that I dedicated myself to music after that but there weren't a lot of places to play in town and there never seemed to be any way of doing music for a living," he says. "Plus, after I left school, I spent a few years completely without focus. I felt lost. I joined the Navy for long enough to know it wasn't for me and did pretty much every odd job that you can mention."
In his mid-twenties Simpson formed his first band aimed at getting his own songs heard, but more conventional forms of work, including moving to Utah with Union Pacific, got in the way. Still, he wrote songs and played guitar in fits and bursts until the move to Nashville forced him to focus completely on his music.
"I've always tried to keep songs as simple as possible," he says. "Three or four chords behind a lyric that gets straight to the point is the blueprint, I suppose. And I don't spend a lot of time on a song because if it's forced it's probably not very good."
There's certainly nothing forced sounding about either of Simpson's albums so far. For High Top Mountain he teamed up with seasoned session musicians including pianist Hargus "Pig" Robbins and steel guitarist Robby Turner, at the suggestion of producer Dave Cobb, who told Simpson that if he wanted to make the album sound like the old albums from the heyday of Waylong Jennings and Tompall Glaser, he should record with the players who made them. Cue Simpson sitting in a vocal booth, playing guitar and looking through a glass partition at a group of Nashville legends. The experience, he says, certainly made him his up his game.
Metamodern Sounds in Country Music was made with Simpson's own band and presents the tough, concise sound UK audiences can hear when he tours with his band in late September, following a solo date at the Southern Fried festival, in Perth, on Saturday, July 26. It will be the fourth trip over here this year for Simpson, who finds the audiences here wonderful if disconcerting.
"The first time I played over here, the audience were so quiet that I thought I was bombing," he says. "I thought they hated it but they were just listening. It's the most appreciative reception I've ever had. But the UK generally has been good to me. I feel accepted here and I certainly won't take that for granted."