(UK added due to their interest in this subject).

There was a prior conversation about area code assignment.

In November 1951 Englewood NJ got the first Direct Distance Dialing
for plain station-to-station calls. Locations dialable were limited
to the following locations. For cities, it was generally the city
only and perhaps a few adjacent suburbs, not the whole metropolitan
area. The cities below represent only nine states and only a small
portion of the states.

New Jersey--central and northern only, not southern
New York City (dial 11)
Nassau County (western) 516
Westchester County, NY (lower) 914
Boston 617 (includes suburbs)
Chicago 312
Cleveland 216
Detroit 313
Milwaukee 414
Oakland 415
Philadelphia 215
Pittsburgh 402
Providence 401
Sacramento 916
San Francisco 318

Note that some of the exchanges dialable were still served by manual
switchboards. When such a manual exchange was dialed, a special
display lit up for the inward "B" operator showing the desired number
and she plugged in accordingly.


As mentioned, a considerable part of making DDD available was giving
everyone a dialable seven digit local phone number that was unique
within an area code. Further, people in small towns with four or five
digit numbers would continue to dial those numbers for local calls.

Step offices would require dialing an access code of three digits.

Also needed to be implemented was automatic routing and automatic
message accounting (AMA). Some calls would be handled by a separate
toll switch.

Coordination was needed with Independent companies.