It's the first time convention has been in Philadelphia. About 800 people from as far away as Japan and Germany are taking part in the performances and dancing at the Philadelphia 201 Hotel.
For the uninitiated, square dancers pair off and execute one of dozens of moves announced by a "caller."
Betsy Gotta of North Brunswick, New Jersey, is a caller coach.
"Each command, basically — it's in English, but it doesn't have meaning in English. It has a meaning in the language of square dance," Gotta said.
"One command might be, 'Head Ladies Chain Across.' And what it means is, the ladies are going to walk by each other and be turned around by the gentlemen on the other side and exchange places," she said.
Convention coordinator Dane Bragg of Easton says it's an open and welcoming group.
"Many of us in the community are straight," Bragg said. "It started at a time when straight and gay recreational activities were separate. And the world has fortunately changed. So it's not so gay anymore."
The convention runs through Sunday, with several performances open to the public.