<span>Theodore Roosevelt, 26th
President of the United States, was one of the most important
and effective environmental leaders in American history. Beginning in the 1880s and
culminating with his Presidency (1901-1909), his leadership of the emerging American
conservation movement was instrumental in preserving hundreds of millions of acres of natural
and historic treasures, including forests, wetlands, endangered species, native ruins, and “natural
wonders” like the Grand Canyon</span>
A topic is like a title of a book and a Unit is like the chapters in the book.
