Ancestry.com. Rio Grande do Sul, Brazil, Miscellaneous Records (Civil Registration), 1748-1998 [database on-line]. Lehi, UT, USA: Ancestry.com Operations, Inc., 2016.Original data: Brazil, Rio Grande do Sul, Miscellaneous Records, 1748-1998. Salt Lake City, Utah: FamilySearch, 2013.
This collection consists of slave records, notarial records, and copies of some of the state's civil registration from the Arquivo Público do Estado do Rio Grande do Sul.
You can learn more about this collection at the FamilySearch website.