I think this notion comes from the general feeling that things were more libertarian in the past, which is true. but you have to go back to before the civil war to really see it.
the united states has gone through 3 phases in terms of government. first was the constitutionalist republic from 1787 til the civil war, which was fairly libertarian in most of its policies compared to today. then civil war until the depression, and finally the depression until present day. each government has been legally distinct in its dealings, and each has been less libertarian than the one before it.