Where once the union had acquiesced to the prejudices of its English-speaking members by supporting the imposition of an alien tax on immigrant workers,after 1897 the United Mine Workers made a determined effort to enlist Italians and Slavs in its ranks.
Where once the union had acquiesced to the prejudices of its English-speaking members by supporting the imposition of an alien tax on immigrant workers, [after 1897状语] [the United Mine Workers主语] [made谓语] [a determined effort宾语] [to enlist Italians and Slavs in its ranks宾补].