Today in 1878, the New Haven District Telephone Company of New Haven published the world’s first telephone directory. It listed the names of about 50 subscribers.
In November 1878, the company, by then renamed The Connecticut District Telephone Company of New Haven, Connecticut, issued the world's first telephone book. It contained the names and addresses of 391 subscribers who paid $22 per year for the service. There were no phone numbers, but there were advertisements (for physicians and carriage companies, for example) and listings of businesses in the back of the book.
The directory included also tips on placing calls and the proper behavior. Because anybody could be on the line at any time, customers were asked not pick up the telephone unless they want to make a call and to be careful about what others might hear. “Any person using profane or otherwise improper language should be reported at this office immediately.”