Since the bald eagle was fully listed under the Endangered Species Act in 1978, the number of nesting bald eagle pairs and productivity (number of young fledged per nest) have been monitored throughout the lower 48 states. This effort has produced an excellent data set.  This information was used to develop the map and chart in the above links.  Follow these links to see how bald eagle numbers have responded since DDT was banned and the Endangered Species Act was passed.