My interest in the Porterfield name derives from my maternal grandmother Juanita Porterfield. Early on I learned of a book entitled The Porterfields written, that traces the roots backs to Scotland.  

As surname variations go, Porterfield seems to be a very dominant spelling. Other different surnames seem to largely be one-off variations - they did not continue multiple generations. 

Some early official records in Latin use a spelling of Porterfeild or Porterfeilde.

There is one family in America that seems to be have original had the name Bodyfield, but adopted the name Porterfield. This line shows no DNA connections to other Porterfields in North America

The earliest male progenitor of the Porterfields appears to be a Norman knight named Alanus De Porter who was alive in the latter half of the 12th century. The first use of the name Porterfield is a number of generations later near the beginning of the 15th century in the name of Robert Porterfield. The early Porterfields were associated with a Porterfield estate in Renfrewshire. In 1554, John Porterfield acquired the estate of Duchal near Kilmacolm from Lord Lyle. Other Porterfields had many other lands in Renfrewshire and Ayrshire, Scotland in days past.

The Porterfield surname originated in Scotland and still found there today. The largest concentration today is in the United States, with significant populations in Canada, and Australia.  There also are Porterfields in Ireland largely as a result of the Plantations of Ireland in the 16th and 17th century.