The ancestors of the Amish came from Germany in the 18th century , and now most of the Amish live in Pennsylvania ( Lancaster County ) and Ohio , in the United States . Certain Mennonite churches have a high number of people who were formerly from Amish congregations . Although more Amish immigrated to America in the 19th century than during the 18th century , most of today 's Amish descend from 18th century immigrants .