Question: what was the first chain of hamburger resturants in the united states
[{'answer': 'White Castle', 'provenance': [{'wikipedia_id': '54923', 'title': 'Fast food restaurant', 'start_paragraph_id': 2, 'start_character': 79, 'end_paragraph_id': 2, 'end_character': 91, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '54923', 'title': 'Fast food restaurant', 'start_paragraph_id': 7, 'start_character': 0, 'end_paragraph_id': 7, 'end_character': 1110, 'bleu_score': 0.8223311826627341, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4124542518936062307}, 'section': 'Section::::History.:United States.\n'}]}]