John Francis is an American environmentalist nicknamed the planetwalker. Born in Philadelphia, the son of a West Indian immigrant, he moved to Marin County, California as a young man. After witnessing the devastation caused by the 1971 San Francisco Bay oil spill, he stopped riding in motorized vehicles, a vow which lasted 22 years from 1972 until 1994. From 1973 until 1990, he also spent 17 years voluntarily silent. During this time he earned a Ph.D. in land management and traveled extensively, walking across the entire width of the lower 48 states of the USA as well as walking to South America.