This case involved the application of the Endangered Species Act of 1973 to a nearly completed $100 million dam on the Little Tennessee River. The dam would have endangered the survival of the snail darter, a previously unknown species of perch which was discovered after litigation over the dam had already begun. There are approximately 130 known species of darters. The district court declined to enjoin construction of the dam, largely because Congress had continued to appropriate money for the dam despite the snail darter problem, and also because the dam was so near completion. The court of appeals reversed, and the Supreme Court granted the government's petition for certiorari