Civil Disobedience is Thoreau's most famous essay; it was written after Henry, protesting slavery and the Mexican War, was put in jail overnight for refusing to pay his poll tax. Someone paid the tax for him -- ending his protest abruptly, so he put his opposition in writing, creating a document that later influenced both Gandhi and Martin Luther King. In occupied Denmark in the 1940's it was read by the Danish resistance, in the 1950's it was cherished by people who opposed McCarthyism, in the 1960's it was influential in the struggle against apartheid in South Africa, and in the 1970's it was discovered by a new generation of anti-war activists.
"It is not desirable to cultivate a respect for the law, so much as for the right. The only obligation which I have a right to assume is to do at any time what I think right.""If a thousand men were not to pay their tax-bills this year, that would not be a violent and bloody measure, as it would be to pay them, and enable the State to commit violence and shed innocent blood. This is, in fact, the definition of a peaceable revolution, if any such is possible."