A later group of Germans who had come from the Russian empire, settling in the late 19th century, took root in Wisconsin and spread westward across the Great Plains region; this group spoke German for several generations after the Pennsylvania Dutch had thoroughly Americanized themselves, theologically as well as linguistically. These immigrants did not participate in the Mercersburg/Ursinus struggle; their theological persuasion was decidedly confessionalist, holding to a fairly strict interpretation of the Heidelberg Catechism. So strong were the convictions of some that a few churches in that group, most of which were in South Dakota, defected immediately prior to the 1934 merger, influenced by such strict confessionalism, a belief in biblical inerrancy, and a fear of losing their Reformed roots. That group retained the name Reformed Church in the United States.