Texas is interesting because you can see "sink marks" where there are urban areas.
I wonder why Northern New England, Northern Appalachia and Florida are faith deserts.
John Wesley suggested that the optimum size for a church is 150. I wonder if that means families. The tension is ownership/investment vs. resources. There are only so many great preachers to go around and large churches can support many ministries.
Another hypothesis is that "less religious" areas are more likely to zone church facilities into "church ghettos" where they are mostly out-of-sight. You cannot miss these churches on Indiana Highway 66. Some of them are only 40 feet away from the pavement.