The billboard said Monster Mike Welch was the main attraction. A 15-year-old blues musician from Lexington, Mass., Monster Mike has a hot hand on the neck of an electric guitar. And those who knew his name came to hear music.

But Saturday night is dancing night, so when Monster Mike and his three backup musicians started winding out blues standards at the Blue Goose Dance Hall in Northport, the main attraction was really the dance floor and the heat of rocking bodies on a cold night.

There was a couple doing swing dances. Another doing ballroom. Teens huddled in a throbbing mass of arms and legs. One guy, who moved like a cat thrown in a bucket of water, danced alone. Three children stood right in front of Monster Mike and jiggled, wiggled, frolicked and screamed.

“It’s the neatest thing about this whole operation — just watching the kids,” said Howard Gallagher.

Gallagher, who coordinates Mid Coast Dance Club at the Blue Goose, has booked four other acts this year at the rustic dance hall, which used to be a roller-skating rink. All the dances have been fund-raisers for local organizations. All are chem-free, smoke-free, open to anybody of any age who wants to shake his or her booty.

With an 85-by-55-foot maple floor, a 12-foot ceiling, and a disco ball, the Blue Goose is a perfect spot for live music and lots of grooving bodies. More than 250 people crowded in to hear Monster Mike. It didn’t matter that blues music is generally too fast or too slow to move to. The dance was the thing.

Gallagher could often be seen through the evening flinging his arms and stomping his feet in dance. When he wasn’t in the boogie mode, however, he talked with people. As four teen boys were leaving the building, Gallagher called out to them, “Thanks for coming by, you guys.”

“Oh, we’re coming back. We’re just going out to have a cigarette,” one of the boys answered.

“You like it?” Gallagher asked about the music.

“Yeah!” they answered.

Inside the Blue Goose, Earth John, a 17-year-old senior at Camden-Rockland High School, had kicked off her shoes and was dancing in her black nylons.

“This is, like, my favorite,” she said of the event. “A lot of kids like to thrash and head bang, but this feeds my soul.”

If dancing was, in fact, the main attraction, the next attraction was watching the dancing. During a slow number when most people grabbed a partner, one young woman flitted solo among the couples, moving her arms like a willow tree. A man in his 60s sidled up to a woman in her 40s and asked if she wanted to dance. The answer was no, and he moved on. During a slide-guitar number, another woman moved her long black dress like a billow in front of colored spotlights.

On the edge of the dance floor, a man dressed in pink tails and a woman in a black dance skirt and orange top created a new style of dance. Sometimes they were back to back, sometimes front to back, sometimes nowhere near each other. Occasionally, she would drop to the floor on one knee as if proposing marriage. Then she would rise and kick her limber leg into the air. They danced nearly every dance.

Just before they left for the evening, the couple took a moment to rest.

“It’s a nice facility and good music,” said the man.

“And it’s not contredansing,” she added.

From the very first song, the dance floor was constantly busy. More than two straight hours of music passed before Gallagher took a break to talk about his dream of creating a dance hall for all ages and interests. Since the arrival of the community radio station WERU, and the folkie influx at the Left Bank Cafe (both in Blue Hill), bands are increasingly willing, if not eager, to come to Maine, said Gallagher. And places like the Blue Goose are safe, lively, and easy to get to.

So what if the musicians have to use the bathroom as a dressing room.

So what if there are only soft drinks and ice cream at the bar.

So what if it’s two degrees outside.

These people are happily suffering with dance fever.

And those who come because it’s a fund-raiser like making contributions to local organizations (this night for the YMCA, Friday for Mid-Coast Family Planning).

“This is so important for us to be doing this,” said Beverly Kocenko, as she walked by Gallagher to take a break outdoors. “It’s so healthy.”

Gallagher beamed. Kocenko’s response is exactly what he has hoped for. And within minutes, both were back on the Blue Goose dance floor enjoying the main attraction.