turing test

Prompt

During the construction of the Transcontinental Railroad in the United States, what was the specific, verifiable date on which the Union Pacific Railroad, using the CPRR's smaller gauge as a standard, first successfully laid track that incorporated the newly standardized 'American Standard' gauge of 4 feet 8.5 inches (1435 mm), and what was the exact location of this event? Provide the date and the location. Note: The first major use of this gauge as a de facto standard in the U.S. is often cited from a specific 1863 date, but the successful track-laying at the designated location is recorded in a specific historical telegraphic dispatch from the field.