The Silent Valley is located in which one of the following States?

Silent Valley National Park is located in the Palakkad district of Kerala, India. It is situated within the Nilgiri Hills and constitutes the core area of the Nilgiri Biosphere Reserve. The park is famous for its unique tropical evergreen rain forests and is home to the endangered lion-tailed macaque. The Kunthipuzha River flows through the entire length of the valley from north to south. It became a focal point of environmental conservation in India during the 1970s through the "Save Silent Valley" movement, which successfully protested against a proposed hydroelectric project that threatened the valley's ecosystem. The park was formally inaugurated in 1985.