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In the early days of the telephone, knowing who had them and what their numbers were quickly became a problem.

The first telephone directory in the U.S. was published in 1878 in New Haven, Connecticut.

It wasn’t a big list — there were only 50 subscribers.

A little later, a directory also came out in San Francisco, with about 170 names.

Now, there are 270 million phone lines in the nation, about a third of them residential and directory services are well established.

The growing problem today is keeping track of the phone numbers of the more than 255 million cell phone users.

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