Why was the snail darter endangered?

The snail darter (Percina tanasi) is a small, freshwater fish in the family Percidae. It is native to the southeastern United States, principally to a stretch of the Little Tennessee River in Tennessee and Alabama, and a few surrounding river systems. The snail darter is an endangered species, mostly because of the construction of the Tellico Dam.

The Tellico Dam was a hydroelectric dam project of the Tennessee Valley Authority (TVA) that began in the early 1970s. The dam would flood the snail darter's only known habitat, and the TVA sought an exemption to the Endangered Species Act of 1973, which protected the snail darter.

Environmentalists sued to stop the construction of the dam, arguing that the snail darter had a right to exist and that its extinction would be a loss to the ecosystem. The case went all the way to the Supreme Court, which ruled in favor of the environmentalists in 1978.

As a result of the Supreme Court's ruling, the TVA was forced to abandon the Tellico Dam project. The snail darter was saved from extinction, and it remains one of the most famous endangered species in the United States.