Sentence:  Was it supposed , perchance , that A + M ( vocational training , that is ) was quite sufficient for the immigrant class which flooded that part of the New England world in the post Civil War period , the immigrants having been brought in from Southern Europe , to work in the <WSD>mills</WSD> , to make up for the labor shortage caused by migration to the West ? 
Meaning of the word marked with <WSD> tags:  a plant consisting of one or more buildings with facilities for manufacturing