John McEuen, multi-instrumentalist and a founding member of the Nitty Gritty Dirt Band, keeps a scathing, late-1960s Billboard magazine review in a special place. The article doubted the roots-laden California outfit would ever score a record deal.

“It (hangs) in a frame with our first platinum album,” said a chuckling McEuen over the phone.

The band, which twanged Americana decades before the genre existed, has gone on to prove the article wrong many times over. As the group continues celebrating its 50th anniversary with a concert tour — it lands March 31 at Symphony Hall — the irony isn’t lost on McEuen, and neither is his thankfulness.

“There’s a sense of gratitude that we’re able to do something only the four of us could do,” McEuen said, quickly praising his bandmates Jeff Hanna, Bob Carpenter and Jimmie Fadden. “Jimmie amazes me with his harp and drums at the same time. Bobby kills on Jeff’s song ‘Broken Road,’ and Jeff has never played better. I think it’s the best level we’ve been at, and we have a 50-year span of music to draw from.”

Throughout those 50 years, the Nitty Gritty Dirt Band’s journey couldn’t have been more colorful. In the early days, they opened for such polar opposite acts as comedian Jack Benny and psychedelic rockers the Doors. They shared screen time with Clint Eastwood and Lee Marvin in the 1969 musical comedy “Paint Your Wagon.” In 1977, the Nitty Gritty Dirt Band became the first American group allowed to tour the Soviet Union. Today the band’s reading of Jerry Jeff Walker’s “Mr. Bojangles” resides in the Grammy Hall of Fame.

“That’s exciting,” McEuen said of the latter accolade, “but one of the qualifications for that is the record has to be at least 40 years old. I was like, ‘Oh, no! I thought it was 15 years old!’”

Those highlights only scratch a little dirt off the Dirt Band’s historic surface. Arguably one of its most important contributions could be called the audio bible of Americana: 1972’s “Will the Circle Be Unbroken.”

According to McEuen, the success of the band’s 1970 disc “Uncle Charlie & His Dog Teddy,” which yielded “Mr. Bojangles,” gave them the credibility to tackle an ambitious, triple album like “Will the Circle Be Unbroken.” The landmark recording found the Nitty Gritty Dirt Band sharing a Nashville studio with old-school bluegrass and country-western luminaries, including Roy Acuff, Mother Maybelle Carter, Earl Scruggs, Doc Watson, Merle Travis and others. Country classics, traditional tunes and original songs penned by the performers were captured on tape in one or two takes.

“We were worried about (recording with) these stalwart, iconic people,” McEuen said, “but getting in the studio, we found out that’s what they did. They liked to record. They were happy to do music together, and they were big fans of each other, which made us at ease.”

Years of touring, and landing on the pop and country charts continued. As McEuen watched the band's star rise, it took place almost in tandem with the growing career of his longtime friend, actor and comedian Steve Martin.

As teens, the pair worked together at Merlin’s Magic Shop at Disneyland, and McEuen eventually taught Martin how to pick the banjo. Later, once the Dirt Band began casting a melodic spell of its own, Martin would often open for the group. McEuen’s brother William managed both the band and Martin.

“He got a review in the Los Angeles Times that said, ‘Somebody should tell the opening comedian that jokes should be funny,’” McEuen recalled.

By the mid-1970s, American audiences were getting Martin’s humor. When the comedian released the hit novelty single “King Tut” in 1978, the Nitty Gritty Dirt Band rocked like Egyptians while backing Martin.

McEuen said Martin’s perseverance and continuous output continue to inspire. McEuen produced Martin’s 2009 bluegrass album “The Crow: New Songs for the 5-String Banjo,” which won a Grammy for best bluegrass album the following year.

Stories of his friendship with Martin inevitably veer to the band’s early 1970s stint at Atlanta’s defunct Great Southeast Music Hall. McEuen said that’s where a show’s success was gauged by “how squishy the rug was from the beer at the end of the show.”

McEuen remembers him and Martin walking back to the venue between shows, marveling at the line stretching around the building.

“Steve said, ‘I never thought it would get this good,’” McEuen said, laughing. “And it had. That crowd gave us that footprint in Atlanta that we’re really happy to have.”

McEuen’s own local footprint has grown, thanks to the fact his daughter Noel and her family call Alpharetta home. Surely the local cheering section will provide even more hoots and hollers as McEuen rips on mandolin, banjo and acoustic guitar during the upcoming Atlanta show billed as “50 years of Dirt.”

Last year, the band’s 50th anniversary received a push with“The Nitty Gritty Dirt Band: 50 Years and Circlin’ Back” PBS special. Recorded live at the Ryman Auditorium in fall 2015, the band jammed with special guests including Vince Gill, Alison Krauss, Jackson Browne and John Prine.

“When we were on that Ryman stage doing that show,” McEuen said, “I think we had become what we were emulating. It was like we had arrived.”

Amid the Americana boom, McEuen seems to welcome his arrival at elder statesman status in the burgeoning genre. His 2016 solo album “Made in Brooklyn” had McEuen culling musician friends, including Martin, and digging up his roots like he has since the late 1960s.

“Americana is a place to go for a lot of people who might not have found a niche,” McEuen said. “And now it’s finally become something that somehow has a nomenclature of a definition of a certain type of sound.”

CONCERT PREVIEW

Nitty Gritty Dirt Band

8 p.m. March 31. $29.50-$69.50 plus fees. Atlanta Symphony Hall, 1280 Peachtree St. N.E., Atlanta. 1-800-745-3000, 1-866-448-7849, ticketmaster.comnittygritty.comjohnmceuen.com.