The historical significance that impacted Theodore Roosevelt involved his role as a key figure in the Progressive Era. Roosevelt's administration prioritized reform in areas such as antitrust laws, labor rights, and conservation of natural resources. His engagement in social issues and his leadership in the Spanish-American War elevated the United States' status on the global stage. Roosevelt's policies and his charisma helped shape modern American politics, reinforcing the idea that the government should play an active role in ensuring the welfare of its citizens.