[1] Las Mercedes was named in honor of both the Virgin Mary and Doña Mercedes Delgado Manso, the wife of the then mayor of San Lorenzo and a descendant of Don Sebastián Delgado Manso, one of the founders of the city of Caguas.

[2] Although the current structure of Las Mercedes officially dates to 1887, it was built at the site of a former chapel originally named Hermitage of Hato Grande (Ermita de Hato Grande, also known then as La Ermita del Hato) that was built in 1737, at a time when San Lorenzo was a newly settled small village.

Records from the Caguas City Hall show that the architecture of that hermitage resembled that of Porta Coeli Monastery Church in San Germán.

The hermitage was upgraded in size with the current walls and façade finally being added in 1887 by state architect Pedro Cobreros.

The church is one of the best examples of late 19th century Neoclassical architecture that would set a trend in the religious architecture in the island,[2] and for this reason it was added to the National Register of Historic Places in 1983 and to the Puerto Rico Register of Historic Sites and Zones in 2000.