Lord Acton, the famous 19th-century historian of liberty, is quoted as
having written that liberty ?was that which *was not*, until the last
quarter of the eighteenth century in Pennsylvania.?  [Isabel Paterson,
*The God of the Machine* (1943; Caldwell, Idaho: Caxton Printers,
Ltd., 1964; 2nd prtg, 1968), 305]  I have never been able to find
where Acton wrote that.  Could you provide me with a citation?  Please
provide enough information so that it would not only be findable but
also "footnote-able."  If you think he did *not* write that, please
let me know why you think so (your credentials, your search methods,
or whatever you think makes your answer definite).  Thank you, Steve
Jolivette

The phrase doesn't seem to exist in any of Acton's writings or
lectures; a search for the phrase (on the web, exact phrase in quotes)
returns only one result, where it is given with no citation. This
doesn't necessarily mean that he didn't SAY it, of course...there's
always the possibility that it was a comment not written down but
spoken, and recorded by someone else. However, the lack of any more
contemporary reference rather leads one to suspect that the
attribution was spurious; it's quite common for quotations to be
falsely attributed to famous figures, especially when it SOUNDS like
something the person would or "should" have said. It does, however,
seem not too far from the following (from a lecture delivered in 1877,
"On The History of Liberty in Antiquity":

Liberty, next to religion has been the motive of good deeds and the
common pretext of crime, from the sowing of the seed at Athens, 2,460
years ago, until the ripened harvest was gathered by men of our race.
It is the delicate fruit of a mature civilization; and scarcely a
century has passed since nations, that knew the meaning of the term,
resolved to be free.

In the above passage, the "nations that...resolved to be free"
referred to are obviously the United States and France; this comes
closest, in spirit, at least, to the quotation you're inquiring about.

Thank you for the comment, raketemensch-ga.  Actually, I take it as an
answer.  If you are a Google Answers Researcher, please post it as as
an answer and take my payment ($10, if I remember).