Twenty-five years ago, an unsigned band out of Athens, Georgia, named Drive-By Truckers recorded the equivalent of a tree falling in the forest with no one there to hear it. A very big tree.

It was a thematic, double-album colossus loosely about, as one of its signature songs put it, “the duality of the Southern thing,” and it was accomplished exclusively between the hours of 6 p.m. to 6 a.m. due to the sweltering conditions in their makeshift studio in a second-floor uniform shop.

Combining the genre with which they were most closely identified and the concept first pioneered by The Who with “Tommy,” they called it “Southern Rock Opera,” though its motif owed more to The Replacements than Athens’ most famous musical sons, R.E.M. When it was done, with finances drained, they were only able to manufacture and distribute the album after soliciting individual investors — in a pre-Kickstarter world — allowing them to raise $23,000, produce less than 5,000 copies and buy a used van for a hoped-for tour.

The buzz “Southern Rock Opera” generated among fans and critics alike was immediate; the band was signed by Mercury Records, and the record was re-released for worldwide distribution with Mercury subsidiary Lost Highway Records in 2002.

A short time later, Drive-By Truckers was named Band of the Year by industry heavyweight No Depression. An 11-album, decades-long career of spectacularly ragged glory (apologies to Neil Young) has ensued. More than anything else, think a heavier-sounding “Exile on Main Street” period Rolling Stones, an often-relentless onslaught of purposefully sloppy guitars and occasionally unhinged vocals, a squall of sound with a Southern twang, but composed with the densely packed, hyperintelligent and socially conscious storytelling of the band’s two founders, front men and constants: Patterson Hood and Mike Cooley.

Drive-By Truckers recently brought their ambitious anniversary tour, “Southern Rock Opera Revisited,” to Portland’s State Theater. And although I’d seen their delightfully raucous performances live several times before, my expectations were still especially piqued by the unapologetically epic concept and nature of the album to be reproduced. Here in Portland, I wanted to try to do something in the way of a pre-show activity to try to get into the Southern groove.

Alas, despite its well-deserved reputation as a foodie city, to my knowledge Portland lacks a true Southern restaurant. I set my sights on the nearest facsimile I could conjure, the “fine diving” Congress Bar & Grill, for its locally renowned spicy fried chicken sandwich (and favorite full-wall photo from “The Big Lebowski”).

Unfortunately, it’s also the nearest proximity-wise to the State, and by my 6:15 arrival was already filled with fellow concert-goers. Instead, we quickly decamped a block down High Street to the always-reliable and homey Little Tap House.

Back at the theater — now solo, after counseling my wife that the anticipated three-guitar thunderstorm might not exactly be to her liking — there was just enough time to grab a beverage, a creamy dark lager brewed by Sacred Profane, a relatively new addition to Portland’s rich craft beer scene (I highly recommend the entirety of their brewhouse options: dark and pale lager).

Then I nestled in just a few body-widths back from the stage on the GA floor. I do not do ear plugs; I’d no sooner restrict the ambient sound booming out of loudspeakers at a concert than I would partially cover my eyes while viewing paintings at a museum. Volume is a defined part of the presentation.

As on the album, DBT opened with the song “Days of Graduation,” a gruesome narration over eerie accompaniment of a car crash death in which the length of the song “Freebird” becomes a significant gory detail. As much as the band is capable of revving up the raunchy-sounding rowdiness — as they would on subsequent tunes such as “Ronnie and Neil,” “Guitar Man Upstairs” and “Shut Up and Get on the Plane” — this is unmistakably an album with dark overtones. The inherent conflict of Southern pridefulness viewed through the unblinking eye of both civil rights-era and modern history is inescapable.

At one key point of the show, during their riveting re-creation of “The Three Great Alabama Icons” — a number possibly like no other “song” you’ve ever heard before — Hood changed the lyric cited earlier to “…the duality of the American thing,” a certain sign that Drive-By Truckers resolve to a decidedly and defiantly blue state vantage point despite emanating from their red-state locale.

In all they played 18 of the 20 tracks from the original release, while mixing in numerous other catalog highlights plus a couple of smart encore covers, in a draining but rousing two-and-a-half-hour showcase of blunt musical force. Yet, as I made my brisk walk home through falling snow, I did have an honest realization: I thought it could’ve been a little louder.

Awaking still in the mood for another form of Southern hospitality, I mobilized to Bayside’s Wilson County Barbecue, where I brunched on tasty chicken and waffles and what turned out to be an even more filling side order of loaded grits. And taking a break from the legion of superb locals, I washed it all down with a Miller High Life.

Does anybody know why Miller, seemingly alone among old-school domestic brews, is featured at so many happening Portland establishments as a ridiculously low-cost option? My bartender was as baffled as me, but no less happy to pour a frosty 20-ounce draft for $3 that brought me back to surreptitious parking lot imbibing in high school.

Like this one, my prior Drive-By Truckers concerts have all taken place in the Northeast. Directionally, you might say that’s at least in a marginal southern orientation.

Taking into consideration, however, a band as culturally and attitudinally associated with the sweeping region below the Mason-Dixon Line — discordant as that alignment may be — I’d have to enter it onto my bucket list to experience them another time in an authentic Southern venue. Portland wasn’t quite that, but it is, after all, at least readily identified as being in the small corridor known as Southern Maine.