The Endangered Species Act of 1973 (ESA; 16 U.S.C. § 1531 et seq.) is one of the few dozens of United States environmental laws passed in the 1970s, and serves as the enacting legislation to carry out the provisions outlined in The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The ESA was signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and development untempered by adequate concern and conservation." The U.S. Supreme Court found that "the plain intent of Congress in enacting" the ESA "was to halt and reverse the trend toward species extinction, whatever the cost." The Act is administered by two federal agencies, the United States Fish and Wildlife Service (FWS) and the National Oceanic and Atmospheric Administration (NOAA). 

One species in particular received widespread attention—the whooping crane. The species' historical range extended from central Canada South to Mexico, and from Utah to the Atlantic coast. Unregulated hunting and habitat loss contributed to a steady decline in the whooping crane population until, by 1890, it had disappeared from its primary breeding range in the north central United States. It would be another eight years before the first national law regulating wildlife commerce was signed, and another two years before the first version of the endangered species act was passed. The whooping crane population by 1941 was estimated at about only 16 birds still in the wild.
What was the number of whooping cranes in the wild in 1941?
about only 16 birds