The Reformed Church in the United States (RCUS) is a Protestant Christian denomination in the United States. The present RCUS is a conservative, Calvinist denomination. It affirms the principles of the Reformation: Sola scriptura (Scripture alone), Solo Christo (Christ alone), Sola gratia (Grace alone), Sola fide (Faith alone), and Soli Deo gloria (Glory to God alone). The RCUS is most heavily concentrated in California, Colorado, and South Dakota.