When did "actresses" become "actors"?

[JoeM]

Not much clarification from wikipedia but I think this gives the gist of it:

...The words "actor" and "actress"
The word "actor" may be used to refer to a male or female performer; this was the original use of the term.[1] Some modern style guides recommend using "actor" as a gender-neutral term for both male and females, regarding "actress" as sexist.[2], although this may initially be confusing for readers. Some female performers prefer the term "actress", while others prefer "actor"....

http://en.wikipedia.org/wiki/Actress