Natural Resources Defense Council — Environmental advocacy organization combining legal, scientific, and policy work, founded 1970. nrdc.org
National Wildlife Federation — The largest wildlife conservation organization in the U.S., founded 1936. nwf.org
Earthjustice — Nonprofit environmental law organization, founded 1971. earthjustice.org
Defenders of Wildlife — Founded 1947, focused on protecting native species and habitat, particularly large carnivores. defenders.org
National Audubon Society — Founded 1905, one of the oldest conservation organizations in the country, focused on birds and their habitats. audubon.org
Ocean Conservancy — Founded 1972, focused on ocean health, marine conservation, and reducing marine pollution. oceanconservancy.org
American Bird Conservancy — Founded 1994, focused on conserving wild birds and their habitats throughout the Americas. abcbirds.org