Just ran into this anniversary - the first trans-continental telephone call was placed 100 years ago on Friday 23rd, 1915.
From Computerworld:
This 1915 conference call made history
These days, making a call across the U.S. is so easy that people often don't even know they're talking coast to coast. But 100 years ago Sunday, it took a hackathon, a new technology and an international exposition to make it happen.
The first commercial transcontinental phone line opened on Jan. 25, 1915, with a call from New York to the site of San Francisco's Panama-Pacific International Exposition. Alexander Graham Bell made the call to his assistant, Thomas Watson. Just 39 years earlier, Bell had talked to Watson on the first ever phone call, in Boston, just after Bell had patented the telephone.
A bit more:
By June 1914, the more than 730,000 pounds (331,000 kilograms) of copper had been strung out across the network and engineers started making test calls. But commercial service didn't begin until after the Jan. 25, 1915, ceremonial call. When it did, a three-minute call cost $20.70, the equivalent of nearly $485 today.
If they'd been paying, the participants on that first call would have racked up quite a bill. After Bell and Watson talked, a string of dignitaries including the mayors of San Francisco and New York went on the line. Vail called in from his summer home in Jekyll Island, Georgia, where a special private line had been set up because an injured leg prevented him from going to headquarters in New York. Then U.S. President Woodrow Wilson came on the line from the White House.
It took about 10 minutes just to connect a transcontinental call, because the connection had to be set up step by step with a switchboard operator in each city along the way. The ceremonial call on Jan. 25 took three and a half hours, from 4:30 p.m. to 8:00 p.m. New York time. Then Boston joined in for more conversations -- even one in Cantonese, between the founder of a Chinese telephone exchange in San Francisco and a Southern Pacific Railroad official in Boston.
Later that evening, the line was opened to paying customers. The first call was made by Fred Thompson, at the Stewart Hotel in San Francisco, to his mother, Margaret Thompson, at the Bensonhurst Hotel in Brooklyn. They reported that it sounded just like a local call.
But the transcontinental phone line remained a spectacle throughout the exposition, which ran from Feb. 20 to Sept. 4, 1915. AT&T opened a pavilion where visitors could pick up a phone and hear sounds from across the continent, including musical performances and the Atlantic Ocean.
Quite the event - here is a nice website celebrating the 100th anniversary of the Panama-Pacific International Exposition including the phone call.
