Philosophical foundations
The 1400s through the 1700s : inhabiting a new land
The early 1800s : destroying the frontier
The late 1880s : building an industrial nation
The 1900s through the 1930s : beginnings of the conservation movement
The 1940s through the 1960s : prelude to the green decade
The 1970s : the conservation movement matures
1980s : a conservative backlash
The early 1990s : government retrenchment and public apathy
The late 1990s : the institutionalization of the environmental movement.