Question: when did the first public kindergarten open in the united states
[{'answer': '1873', 'provenance': [{'wikipedia_id': '2840637', 'title': 'Susan Blow', 'start_paragraph_id': 9, 'start_character': 196, 'end_paragraph_id': 9, 'end_character': 200, 'bleu_score': 1.0, 'section': 'Section::::Career.\n'}]}, {'provenance': [{'wikipedia_id': '2840637', 'title': 'Susan Blow', 'start_paragraph_id': 9, 'start_character': 0, 'end_paragraph_id': 9, 'end_character': 720, 'bleu_score': 0.9839344367380701, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 562422418253154096}, 'section': 'Section::::Career.\n'}]}]