Murray Newton Rothbard was an influential American historian, natural law theorist and economist of the Austrian School who helped define modern libertarianism. Rothbard took the Austrian School's emphasis on spontaneous order and condemnation of central planning to an individualist anarchist conclusion, which he termed "anarcho-capitalism".
In the 1970s, he assisted
Charles Koch and
Ed Crane to found the
Cato Institute as libertarian think tank.