One of the leading factors at the time was the use of DDT which caused their egg shells to thin and break before they hatched. Other reasons for their decline were pollutants and contaminates in the water way, which poisoned their food source and hunting.
Bald Eagles are still in danger despite making a comback from the endangered species, many of them losing their lives to hunting, traps, high power lines and destruction of habitat.
Today there are about five thousand nesting pairs and about twenty thousand of the birds in the lower forty states of the United States. They are protected by the Endangered Speciies Act of 1973. And while a great many of these birds live in Alaska, you don't need to go that far to see them. On February 5th, Teatown's Hudson River Eaglefeast takes place where you can see these wonderful birds right here in your own back yard. Visit http://www.teatown.org/eaglefest_2011.htm for more information. And do what you can to support organizations that protect our endangered animals.