[3][4][5] Maguayo 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 Maguayo barrio was 764.

In 2017, after Hurricane Maria destroyed infrastructure and disrupted electrical and water services, residents of Maguayo were getting water from a well that is on the List of Superfund sites (a site containing toxic substances) until officials from the Environmental Protection Agency secured the location.

[13] 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).

[5] Major League Baseball player Edgar Martínez spent his formative years in Maguayo.