Thomas Jefferson’s lasting impacts on the formation of the United States include his role as the principal author of the Declaration of Independence, articulating the core values of liberty and democracy. His vision of a nation grounded in these principles laid the foundation for American identity and governance. Jefferson’s contributions to the Louisiana Purchase expanded the nation's territory, significantly shaping its future. Additionally, his advocacy for the separation of church and state influenced American political thought. Jefferson's complex legacy encompasses his promotion of enlightenment values, advocating for individual rights, and emphasizing the significance of education for a thriving democracy.