Question: where did the union pacific start building the transcontinental railroad
[{'answer': 'on January 8 , 1863', 'provenance': [{'wikipedia_id': '36541', 'title': 'First Transcontinental Railroad', 'start_paragraph_id': 56, 'start_character': 33, 'end_paragraph_id': 56, 'end_character': 52, 'bleu_score': 1.0, 'section': 'Section::::Transcontinental route.:Construction begun.\n'}]}, {'provenance': [{'wikipedia_id': '36541', 'title': 'First Transcontinental Railroad', 'start_paragraph_id': 56, 'start_character': 0, 'end_paragraph_id': 56, 'end_character': 1181, 'bleu_score': 0.8902581227308141, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3870060617368558643}, 'section': 'Section::::Transcontinental route.:Construction begun.\n'}]}]