Águas de São Pedro
Recognizing the importance of the thermal springs in the region, the São Paulo State Government on 19 June 1940 founded the (Hydromineral and Climatic Spa of Águas de São Pedro). Despite this, the city celebrates its birthday on 25 July, the date in 1940 of the founding of the first major building in the city, the "Grande Hotel" (now "Grande Hotel São Pedro"). The municipality of Águas de São Pedro was incorporated by State Law No.233, of 24 December 1948.
Água de Pau
There are various theories as to the origin of the villa's name, "Água de Pau", which literally means "water of wood" (which can be interpreted as "waters where wood exist"). The most recognized story pertains to early settlers whom, upon arriving in the vicinity of the coast, noticed a large ravine emptying into the ocean from a swamp. Another story defended locally is that the name derived from the corruption of the phrase "Água do Paul" ("paul" possibly being a term for swamp or bog), which itself referred to the "Ribeira do Paul", an old ravine that existed in the area behind the older parochial church of Nossa Senhora dos Anjos. The "Paul" has long since disappeared, and the area behind the church has been cultivated over the decades. Nossa Senhora dos Anjos dos Céus was founded, as was the custom, in the center of the faith community and it is likely that this area was an initial settlement for the community.