As technology advanced during the late 19th century, higher technology companies such as Mack Truck and New Jersey Zinc moved to the region as well. As the local industries expanded, immigrants from Middle Europe (primarily Slovakia, Poland, and Hungary) were recruited for the low-skilled positions, and the more established Dutch retained the skilled blue collar and supervisory positions. The Dutch influence on the shop floor was so great that some Slavic immigrants became bilingual in their native language and in Pennsylvania Dutch while they had not yet mastered English.