1880s: Concern for the environment becomes an issue in the United States in the years following the Civil War, when economic development increases rapidly at the expense of natural resources, such as timber. In 1891, President Harrison signs a proclamation that turns a million acres in Colorado into the nation's first forest preserve.

1990s: Forest preservation threatens jobs in the Pacific Northwest, where loggers prohibited from destroying the habitat of the spotted owl face layoffs. Global concern for the environment results in conferences such as the 1992 Earth Summit, held in Brazil. Topics for discussion include global warming and the destruction of the rain forests.

1880s: Naturalist John James Audubon (1785-1851) attains great wealth and fame from his paintings of birds. He works from dead models; disliking the stiffness of stuffed and mounted specimens, he requires many freshly killed birds for each painting.

1990s: The Audubon...