The national percentage of respondents who say that "religion is very important in their lives" is 56%... and that's right where North and South Dakota (lumped together, of course) come in.
The survey used three other measures:
- + Weekly attendance at religious services: 39% National avg.; 42% Dakotas
- - Pray at least once a day: 58% National avg.; 56% Dakotas
- + Believe in God with absolute certainty: 71% National avg.; 79% Dakotas
The higher belief in God figure might be influenced by Native Americans, many of whom believe in God but who value ceremonies more for key occassions than as a weekly event.
h/t Minnesota neighbor Anglicat.