Before the mass urbanization of Manila, the Pasig River served as an important means of transport and functioned as the city's lifeline and center of economic activity.
Some of the most prominent kingdoms in early Philippine history, including the kingdoms of Namayan, Maynila, and Tondo sprang up along the banks of this river, drawing their life and source of wealth from it.
When the Spanish established Manila as the capital of their colonial properties in the Far East, they built the walled city of Intramuros on the southern bank of Pasig River near the mouth.
After World War II, massive population growth, infrastructure construction, and the dispersal of economic activities to Manila's suburbs left the river abandoned.
The banks of the river attracted informal settlers and remaining factories dumped their wastes into the river, making it effectively a huge sewer system.
The increasing pollution in the river was first noticed in the 1930s when it was observed that fish migration from Laguna de Bay diminished.
People ceased using the river's water for laundry in the 1960s and ferry transport declined. By the 1970s, the river started to give offensive smells and in the 1980s, fishing in the river became nonviable. Pasig River was considered biologically dead in the 1990s.
