Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

Though the conservation movement had European roots, many observers maintain that the United States has emerged as the world's leader in environmentalism.

The transcendentalism of the early 1800s and its celebration of the natural world arrived just in time to be trampled underfoot by the ravages of the Industrial Revolution. As forests disappeared under the ax of reckless timber barons, coal became a popular source of energy. Unfettered use of coal in homes and factories resulted in horrific air pollution in cities like London, Philadelphia, and Paris.

In the 1850s, a carnival huckster named George Gale heard about an immense California redwood that was over 600 years old when Jesus was born. Upon seeing the magnificent tree, nicknamed The Mother of the Forest, Gale hired men to cut the tree down so that its bark could be displayed in his sideshow. The reaction to Gale's stunt, however, was swift and ugly: "To our mind, it seems a cruel idea, a perfect desecration, to cut down such a splendid tree ... what in the world could have possessed any mortal to embark in such a speculation with this mountain of wood?," wrote one editor.

The growing realization that human industry was obliterating irreplaceable wilderness -- and endangering human health -- resulted in the earliest efforts at managing natural resources. In 1872, Yellowstone National Park was created, the first of what became one of America's best ideas: a network of national parks that were strictly off-limits to exploitation.

According to paragraph 4, what was the earliest milestone of green history in the USA?