This study, the first comprehensive look at IRS data on more than 26,000 environmental and conservation organizations 8,000 of which had revenues of $25,000 or more reveals a core of prominent national organizations and a larger, more rapidly growing universe of regional, local, and other specialized groups. Taken as a whole, the environmental movement expanded in number of organizations, members, and in total revenues almost every year since 1960. It focused less on advocacy than on projects and education, and was younger, more densely networked, and more dependent upon grants and contributions than was the nonprofit sector in general.