Question: what had ellis island become the site of by 1891
[{'answer': 'federal immigration station', 'provenance': [{'wikipedia_id': '9806', 'title': 'Ellis Island', 'start_paragraph_id': 32, 'start_character': 125, 'end_paragraph_id': 32, 'end_character': 152, 'bleu_score': 1.0, 'section': 'Section::::History.:First immigration station.\n'}]}]