[3] Although San Andres has only a small land area, it is the second most densely populated district in Manila, as of 2020, after Santa Ana.

The majority of the district's population live just above the poverty line, mostly composed of post-World War II settlers from various provinces while the original inhabitants were middle or lower-class migrant families who had formerly settled in Tondo but found the rough working-class lifestyle less suitable for raising children.

The influx of settlers into the district was unregulated, resulting in a lack of urban planning as evidenced by irregular buildings, narrow roadways, and large blocks of houses accessible only through meter-wide alleyways.

Elderly residents of Singalong believe that the area's name was derived from a Tagalog word for a cup fashioned from bamboo.

In the Spanish colonial era, Spaniards awarded the area to members of the Capuchin missionaries who thereafter converted the native population to Christianity.