Massive pressure from hunting drove down bald eagle populations in the 1800s and 1900s. Then, DDT, a dangerous pesticide that was used heavily in agriculture in the middle of the 20th century, brought bald eagles to the brink by causing a thinning of their egg shells, which caused chicks to die. The effect was so severe that some feared the species' complete extirpation from the country.
But DDT was banned in the U.S. in 1972, and hunting abated, paving the way for bald eagles to come back - and come back they did. In addition to DDT being outlawed, laws were introduced to restrict hunting and trading eagle products, while violators were slapped with hefty fines.