Part of the difficulty of understanding Mark Twain's political outlook is due to terminology and the tendency of politics to corrupt the meaning of everything. As often as you see him called a liberal, he is called a conservative, and sometimes both in the same breath. Critics puzzle about how one person could be champion of workers, owners, and the capitalist rich, while holding views that are antigovernment on domestic matters, antislavery, and antiwar. They often conclude that his politics are incoherent.
Part of the reason for the confusion has to do with the changed meaning of liberalism as an ideology and the incapacity of modern critics to understand its 19th-century implications.
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.The rest of the article is here. It's well worth a read.