 By the 1780s it had become the largest Amish settlement, but declined as families moved elsewhere.The first Amish began migrating to the United States in the 18th century, largely to avoid religious persecution and compulsory military service.The Northkill Creek watershed, in eastern Province of Pennsylvania, was opened for settlement in 1736 and that year Melchior Detweiler and Hans Seiber settled near Northkill.