HeThis transcontinental phone line was a dream several years in the making, started in 1908 by AT&T's president Theodore Vail. The goal was to actually build the phone line in time to celebrate the completion of the Panama Canal. The last pole was installed in Wendover, Utah, in July of 1914, but the official first conversation was postponed until the Panama-Pacific exposition in January the next year. via Gizmodo.
heard a sound that at first he thought was due to some imperfection in the transmission of the voice over the long wire, but in a moment he realized that Mr. Watson had turned away from his telephone to tell the San Francisco audience what Dr. Bell had said, and that the noise he had heard had been the applause of the audience, 3,400 miles away.
On Jan. 25, 1915, inventor Alexander Graham Bell called up his former lab partner, Thomas Watson, in San Francisco, making the first transcontinental phone call in history. "Mr. Watson, are you there?" Watson answered in the affirmative as hundreds of attendees erupted in applause, according to a 1915 edition of The New York Times: