Was Suffolk county N.Y. the 1st county that did not contain a city to get its own area code?

Answer 1

Your question does not make any sense. When area codes went into effect, there were a lot of counties all over the country that did not have a city big enough to get its own code. It all happened at the same time so there were thousands of "firsts."

Answer 2

Lots of counties have area codes without big cities. For the record, Suffolk's 631 only came about in 1999.