Henry David Thoreau (1817–1862) stands among the most influential American philosophers, naturalists, and social critics of the 19th century. Born in Concord, Massachusetts, Thoreau attended Harvard College before embarking on a lifetime of writing and reflection on nature, individualism, and social justice. His seminal work, 'Walden; or, Life in the Woods' (1854), documents his experiment in simple living at Walden Pond, and has inspired countless readers with its meditations on living a life close to nature. Thoreau's essay 'On the Duty of Civil Disobedience' (1849), also known as simply 'Civil Disobedience', criticizes government that unjustly infringes upon the individual's conscience and advocates for nonviolent resistance to wrongful laws, profoundly influencing later social and political thought and activists such as Mahatma Gandhi and Martin Luther King, Jr. Thoreau's literary style combines precise natural observation, personal introspection, and a prophetic voice on issues of social reform. His work continues to be a cornerstone in American literature, appealing not only for its beauty and vigor of expression but also for its sublime transcendental philosophy and advocacy of personal and social liberation.