Jeffrey Tucker has written a nice appreciation of Mark Twain's classical liberal politics:
Twain was born as Samuel Langhorne Clemens in 1835, when the meaning of liberalism was less ambiguous. To be liberal was to favor free enterprise and property rights, oppose slavery, reject old-world caste systems, loathe war, be generally disposed toward free trade and cosmopolitanism, favor the social advance of women, favor technological progress—and to possess a grave skepticism toward government management of anything.
The tradition of thought extends from Enlightenment thinkers like Jefferson through 20th-century Misesians and Hayekians. This outlook on the world might be nearly extinguished from politics today (two flavors of statism), but it was the one embraced by Clemens….
[H]e was a Manchesterite, a liberal of the old school, which, in today's terms, would probably cause him to be classified as a laissez-faire radical or libertarian. He clung to the Whiggism of his family and youth, felt a stronger draw toward Jefferson Davis than Lincoln (but famously and rightly deserted the centrally organized Confederate Army), and championed hard money. He later supported Cleveland in the presidential election of 1884, in part for his support of the gold standard.
Along with Twain's classical liberalism came a strong antiwar position, one which was rooted in Lockean-style love of liberty and opposition to government, not a Leninist-style analysis of the imperialism of finance capitalism.
While this arguably understates the evolution of Twain's views over his lifetime, it's a reasonable summary of the writer's core outlook. There follows a series of illustrations from Twain's books, including a fun diversion into the monetary economics of Tom Sawyer. Tucker also notes that Tom Sawyer and Huck Finn "describe the affairs of a society that is in evolution apart from the state. The state has only one role in the novels and it is entirely negative: it makes and enforces the fugitive slave laws. It is this fact alone that turns Huckleberry and Jim into outlaws fleeing down the Mississippi to find freedom."