Now that email is an office staple, having a phone at your desk is not as essential as it once was. Back when a telegram was the only alternative, however, it's hard to imagine anyone operating without one—especially the President of the United States. But despite the convenience, the Oval Office didn't have a telephone until March 29, 1929—even though phones had been around for more than 50 years.
That's not to say that 1600 Pennsylvania Avenue didn't have any phones. President Rutherford B. Hayes had the first White House telephone installed in 1877. (The phone number was "1.") But the POTUS didn't have a desk phone because previous U.S. presidents believed that using such a device would tarnish the sanctity of the Oval Office. Herbert Hoover was the first to give in, apparently tired of chatting on the phone located in the foyer outside.
Although this happened close to 90 years ago, it seems not much has changed when it comes to service calls. It took longer than anyone expected to get the line working correctly, and even then, it wasn’t right—Hoover complained to aides that his son was unable to get through to the Oval Office phone from an outside line.
All of Hoover’s successors kept the phone on the desk, and possibly revealed more White House business than they intended to: The line wasn’t made private until the Clinton administration.