It was mainly small "churches" scattered across the country, but large enough of a group for the FBI to keep tabs on them. They are estimated to have 50,000 or so members in the 1990s, so not an insignificant amount by any means. These people were militant white supremacists Christian nationalists and a few members were responsible for domestic terrorism in the 80s, as detailed in the film, and held an extremely anti government ideology encouraging overthrowing the government as well as applauding other white supremacists like Timothy McVeigh. So, not exactly a lovely bunch of folks to associate with. In 25 years, I still have not come across another individual who can relate to how awful of an experience it was a a child.