Although there had been wildlife conservation laws in place for decades, by the late 19th century, the passenger pigeon was almost gone, the whooping crane population had plummeted, and many other species were being hunted into extinction. The causes were many - for food, for fashionable clothing, and sometimes just for sport.
In 1900, the Lacey Act was passed, regulating the sale of illegally captured or hunted wildlife across state lines. But the Lacey Act could only do so much; the passenger pigeon went extinct, and by 1941, there were only about 16 whooping cranes left in the wild. The whooping crane became the inspiration for the Endangered Species Preservation Act of 1966, which set aside money to buy habitat for endangered species.
In 1970, the Department of the Interior proposed adding the sperm whale to its list of endangered species, and the Pentagon and Commerce Department protested because the Navy used sperm whale oil in its submarines.
In 1972, President Nixon - not known for environmemtal protection - outlined his environmental agenda to Congress.
"This is the environmental awakening. It marks a new sensitivity of the American spirit and a new maturity of American public life. It is working a revolution in values, as commitment to responsible partnership with nature replaces cavalier assumptions that we can play God with our surroundings and survive."
He specifically asked for a new Endangered Species Act that would provide early identification and protection of threatened species, and treat hunting or capturing endangered species as a federal offense.
In 1973, the House and Senate versions were combined. The Senate passed the bill unanimously, and the House by a vote of 355 to 4.