Why did Henry David Thoreau refuse to pay the poll tax?

Henry David Thoreau refused to pay his poll tax as an act of protest against the United States government’s support of slavery and its involvement in the Mexican-American War.12

As an abolitionist, Thoreau viewed the war with Mexico as an imperialist effort by slave states to expand their power and territory. His refusal to pay the tax was a manifestation of his belief in the supremacy of individual moral conscience over the laws and expediency of the majority. He argued that when a government acts unjustly, a just individual has a moral obligation to resist, even if it results in imprisonment. This philosophy of nonviolent resistance was later detailed in his influential essay, "Civil Disobedience".12