See how U.S. religious landscape has changed in nearly 2 decades - USATODAY.com
h/t San Diego Anglicans.
For South Dakota, the percentage of residents identifying as Catholic or Other Christian is down 17%; Other or No Religion is + 11.
I doubt that the survey controls for Liberal Protestant groups (including many Episcopalians) that are not Christian by any serious definition and belong in the "other religion" category.
Nominal/cultural Christianity is fading and the church's energy and growth are shifting to Africa, Asia and parts of Latin America.
I don't raise this as an "alarm" - it's just what is. Makes for interesting discussion about causes and correlations, and questions about divine purpose and plan.