Puerto Rico Highway 187 (PR-187) is a road that travels from Río Grande, Puerto Rico to Carolina, passing through Loíza. This highway begins at its intersection with PR-3 and PR-66 in Guzmán Abajo and ends at PR-26 in Isla Verde.

Río Grande is a town and municipality of Puerto Rico located on the eastern edge of the Northern Coastal Valley, north of Las Piedras, Naguabo and Ceiba; east of Loíza and Canóvanas and west of Luquillo. Río Grande is spread over eight barrios and Río Grande Pueblo. It is part of the San Juan-Caguas-Guaynabo Metropolitan Statistical Area. A big portion of El Yunque National Forest, including El Yunque's peak, is located within the municipality.