Algarrobo is a barrio in the municipality of Aibonito, Puerto Rico.

[3][4][5] Algarrobo was in Spain's gazetteers[6] until Puerto Rico was ceded by Spain in the aftermath of the Spanish–American War under the terms of the Treaty of Paris of 1898 and became an unincorporated territory of the United States.

In 1899, the United States Department of War conducted a census of Puerto Rico finding that the population of Algarrobo and Llanos barrios was 1,226.

[7] In 2004, Algarrobo in Aibonito was one of the 742 places on the list of marginalized communities (Comunidades Especiales de Puerto Rico); identified as such by the Puerto Rico Office for Socioeconomic and Community Development.

Barrios (which are, in contemporary times, roughly comparable to minor civil divisions)[14] in turn are further subdivided into smaller local populated place areas/units called sectores (sectors in English).