The Maryknoll Sisters arrived in the Philippines in 1926. Three years later, a Maryknoll convent was built in Campo Sioco, Baguio City, originally intended as a vacation and retreat house.
In 1933, seeds of the Maryknoll Convent School were planted when a Syrian mother living in Baguio pleaded with the Sisters to tutor her three children. More pupils were added the following year and thus began what became Maryknoll Convent School, renamed Marishan School in 1977.
In July 1990, a 7.8 earthquake hit Baguio city, damaged the Maryknoll Convent beyond repair, and partly destroyed the school. The devastation in the city prompted the Maryknoll Sisters to examine the community's most urgent need in an ecological context. In November 1991, sixteen months after the earthquake, the Maryknoll Sisters created the Maryknoll Sisters Center for Justice, Peace, and the Integrity of Creation, popularly known today as the Maryknoll Ecological Sanctuary.
Since it formally opened in 1999, it has provided integrated, non-formal earth education to teachers and students in elementary, high and college levels, to religious congregrations, and to the general public. It continues to work towards articulating a new cosmology, or an understanding of the earth and its meaning, gleaned through scientific data, ancient traditions, indigenous cultures, the world traditions, and contemporary spirituality that move us to re-connect both with nature and God's Eternal Spirit.