MANKATO — In the early 1980s, about 15 years after forming City Mouse, Billy Steiner’s band met a crossroads. Wearied from the rigors of the road, changing musical trends and a lineup in perpetual flux, the gritty Mankato group known for its eclectic brand of “good time music” languished in disrepair.

“We were pretty dark and cloudy by that point,” said Steiner, the band’s lead vocalist and harmonica ace. “There was some negativity going on and it just didn’t feel right; it wasn’t what City Mouse was supposed to be.”

By 1986, Steiner had assembled a bevy of affable cohorts (keyboardist par excellence Dale “Hawk” Haefner, acoustic guitarist Ron Arsenault and remnants from the then-defunct Ace in the Whole Band) who helped usher in a new chapter defined by its relaxed continuity.

“A band’s like a marriage,” Haefner said. “It takes a lot of work to stay together. Someone that’s been married that long, one person can start a sentence and their partner can finish it. Music’s a form of communication — after 25, 26 years playing together, all it takes is (a facial gesture).”

The highways have since called the band home to families and less hazardous occupations, but the music remains a vital part of their lives. After a quarter century together, the sextet stands as a brotherhood and partnership in harmony.

“Musically, we breathe together,” Steiner said. “I liked these guys because they were always smiling and happy. We’d hang with them, and they were always in a good mood, always positive, and they still are. That’s why it’s such a kick playing with these guys.”

“Billy kept this whole thing together. And he’s right — we were happy,” Arsenault said. “Happy to be working.”

Saturday at Hooligan’s in Mankato, City Mouse and a legion of collaborators celebrate what was once unthinkable — the band’s 40th anniversary. The triumph also marks the CD release of City Mouse’s 1973 album, a rollicking 10-song collection showcasing a tight, confident band’s diversity. The set is highlighted by soaring vocals from the late Gus Dewey, co-founder of the Gestures, Mankato’s seminal garage rock band.

“I’m really proud of the album,” Steiner said. “It’s all over the place, but we’ve always been that way. And it’s Gus at his peak. He just kills it on every vocal.”

Recently, Steiner and bassist Dave Pengra examined the City Mouse family tree while combing through a thick archival folder containing band artifacts from yesteryear. A different tale was revealed on every page; the two comrades beamed recalling the time basketball great Ray Allen congratulated the band on its a cappella rendition of the national anthem before a Timberwolves game. The memories run deep; in a separate interview, Haefner can even pin the date — 26 years ago — since the band’s last formal rehearsal.

“It used to be never trust anyone over 30,” Pengra, 57, said. “And now this band’s been around for 40 years. I listen to interviews with bands today who have been around for 10 years and they’re ‘veterans.’ Twenty-five years in a band is pretty good; 40 years is ... oh man, incredible.”

No one imagined it would’ve lasted this long. As a teenager, Steiner performed at family gatherings in a duo with his brother, Pete, singing folk songs in the vein of the Kingston Trio and Journeymen. The Beatles and other British bands also served as early influences; by then Steiner was already touring with a folk trio while attending Gustavus Adolphus College.

“That’s all I wanted to do,” he said. “But then it was time to get into something different.”

At a Mankato record store, Steiner spotted his friends from the Gestures, who were listening to the Paul Butterfield Blues Band, a progressive Chicago blues outfit. Steiner heard a foreign sound blaring from the speakers: the electric howl of an amplified harmonica. Mesmerized, Steiner’s musical vision acquired a new trajectory: He wanted to meld his love for blues and honky tonk country with an affinity for singer-songwriters.

“It doesn’t seem odd because they call it Americana now,” he said, “but it was a weird combination at the time: blues, r&b, folk and country.”

Billy’s friend Bob Drengler shared Steiner’s tastes; some of the initial City Mouse gigs featured Steiner and Drengler as a duo, but Bill Denison was also present in the band’s infancy. Through the 1970s, City Mouse was a venerable force in a fertile local music scene, building up a sufficient regional following to require a three-man road crew.

“We were playing everywhere in the ’70s,” he said. “Downtown, out-of-town. We played some good places, but a lot of dives, too. We were broke and staying broke, but you just kept doing it.”

Band members arrived and departed at a dizzying pace — of the 34 musicians who enrolled in City Mouse, Steiner estimates 90 percent played in the band’s first decade. But the group retained a steadfast commitment to its original creed.

“Booking agents in 40 years could never understand us,” Steiner, 61, said. “They love to categorize and they couldn’t with us. We’d do a Merle Haggard tune, then some Muddy Waters and they couldn’t put a finger on it. Some of them would say, ‘Oh, you play that good time music.’ Yeah, we do, and what’s wrong with that? It’s party music.”

When Steiner offered friend and multi-instrumentalist Tim Waters (of Ace in the Whole and the Blitz Boys) a spot as the band’s jack-of-all-trades, he encountered little resistance.

“City Mouse was the hottest thing going when I was growing up,” said Waters, a Mankato native. “It seemed like a great opportunity to get back playing with my friends.”

 Waters’ friends included his Ace in the Whole bandmates, brothers Dave and drummer Mike Pengra, who help shape the most reliable of rhythm combos.

“Mike is a metronome,” Steiner said. “In 25 years, he hasn’t made 10 mistakes.”

“When you look at them, you wouldn’t think they were brothers,” Arsenault said, “but when they start playing together, you just know.”

These days, City Mouse generally limits their roughly 40 yearly appearances to summer festivals, benefits and local gigs. There are also numerous, low-key subgroups — the Fabulous Fatheads, Lost Walleye Orchestra, Ace in the Whole — that feature the members in various formations.

“It’s no longer like it was in ’75,” Haefner said, “wondering where the next gig’s going to be. There’s none of those daily pressures.”

Spurred by a standing offer to record at Catamount Studios in Cedar Falls, Iowa, loose discussions have commenced on the band’s first studio sessions in more than a decade.

“We have to have the most longest longevity for a band, and the least recorded moments,” Arsenault said. “A band that’s been around for 40 years should have, like, 35 albums.”

Steiner, of course, expressed unbridled enthusiasm in the prospect. Finding enough material won’t be the roadblock, he says.

“It’s just a matter of getting everybody’s schedule cleared,” he said. “We could do it real quickly, and I know we’ve got a good record left in us. Why not keep this going?”

So long as it’s still a good time.

“We had a lot of fun,” Dave Pengra said. “You know, we’re still having fun.”