Because we live in a largely free society, we tend to forget how limited is the span of time and the part of the globe for which there has ever been anything like political freedom: the typical state of mankind is tyranny, servitude, and misery. The nineteenth century and early twentieth century in the Western world stand out as striking exceptions to the general trend of historical development. Political freedom in this instance clearly came along with the free market and the development of capitalist institutions. So also did political freedom in the golden age of Greece and in the early days of the Roman era.
History suggests only that capitalism is a necessary condition for political freedom. Clearly it is not a sufficient condition.

Ch. 1 The Relation Between Economic Freedom and Political Freedom, 2002 edition, page 10 - Capitalism and Freedom (1962)