Timeline
1845 – Walden Pond
1847 – George Perkins Marsh
1864 –Yosemite Valley
1864 – The Maine Woods
1866 – Ernst Haeckel
1872 – Yellowstone
1872 – Mining Law
1876 – Appalachian Mountain Club
1886 – Audubon Society
1890 – Yosemite and General Grant National Parks
1872 – Mining Law
1890 – Sequoia National Park
1891 – Forest Reserve Act
1892 – Sierra Club
1893 – Forest Reserves
1898 – Gifford Pinchot
1901 – Sierra Club Outing
1903 – Teddy Roosevelt Visits Yosemite
1905 – Yosemite Under Federal Control
1910 – Lakeview Gusher
1914 – Hetch Hetchy Valley
1915 – John Muir Trail
1916 – National Park Service
1945 – Wilderness Society
1948 – Donora Zinc Works
1949 – Sand County Almanac
1952 – David Brower
1955 – Dinosaur National Monument
1962 – Silent Spring
1965 – Storm King Mountain
1964 – Wilderness Act
1966 – Grand Canyon
1968 – Grand Canyon Dam Plan Killed
1969 – Santa Barbara Oil Spill
1969 – National Environmental Policy Act
1970 – Earth Day
1970 – Clean Air Act
1972 – DDT
1972 – Water Pollution Control Act
1973 – Endangered Species Act
1977 – Tellico Dam
1978 – Love Canal
1979 – Three Mile Island
1980 – Alaska Natural Interest Lands Conservation Act
1986 – Chernobyl
1989 – Exxon Valdez Disaster
1994 – Mono Lake
1994 – Unolcal Diluent Spill
1997 – Julia Butterfly Hill
1998 – David Gypsy Chain
1999 – Luna
2005 – Kyoto Protocol