Catholic Church is the largest religious group in 37 of 51 states (2020); Southern Baptist Convention leads in 9
Largest by adherents, among the groups the census counts one by one: a state split among many Protestant bodies can still show one of them first. The groups' own counts of everyone affiliated, children included; not belief or attendance.
Domestic · Domestic Intelligence · ASARB 2020 U.S. Religion Census · 30 Dec 2020