Murray Newton Rothbard (March 2, 1926 – January 7, 1995) was an American economist of the Austrian School who helped define modern libertarianism and founded a form of free-market anarchism he termed "anarcho-capitalism". Rothbard took the Austrian School's emphasis on spontaneous order and condemnation of central planning to an individualist anarchist conclusion.

An individualist anarchist of the Austrian School of economics, Rothbard associated with the Objectivists in his early thirties before allying with the New Left in the 1960s and eventually joining the caucus of the Libertarian Party.

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