Question: when did california officially become a part of the usa
[{'answer': 'September 9 , 1850', 'provenance': [{'wikipedia_id': '5407', 'title': 'California', 'start_paragraph_id': 34, 'start_character': 142, 'end_paragraph_id': 34, 'end_character': 160, 'bleu_score': 1.0, 'section': 'Section::::History.:Early American statehood period.\n'}]}]