On this day in 1980, the single largest expansion of protected lands in history doubled the size of the US National Park System. As a result, Alaska now has eight national parks, plus numerous monuments and preserves that protect more than 157 million total acres. When President Jimmy Carter signed the Alaska National Interest Lands Conservation Act, the public was granted the right to appreciate stunning locations like the one in today"s photo: the braided river delta of the 51-mile-long Tlikakila River in Lake Clark National Park.