Rachel Carson is an American conservation hero for several reasons.
As a marine biologist, writer, and pioneering environmentalist and conservationist she wrote over a dozen books on the ocean and ocean creatures. Her ground breaking book, Silent Spring, published in 1962 highlighted the dangers of pesticides and their effects on the environment and the ocean. Silent Spring lead to a grassroots environmental movement leading to the creation of the US Environmental Protection Agency.
Second, she worked to create several marine sanctuaries in the US. She also pushed for the establishment of the Endangered Species Act of 1973, which helps protect endangered species in the ocean and on land.
Finally, she was the first to alert the world to the dangers of DDT and worked tirelessly to educate people about the importance of protecting marine habitats and species. DDT was finally banned in the US in 1972. Many species such as pelicans, bald eagles, cormorant, egrets, have rebounded in population since the banning of DDT.
Reference: https://en.wikipedia.org/wiki/Rachel_Carson