A total of forty-one municipalities (Spanish: municipios) are included as part of the San Juan–Caguas–Guaynabo MSA. The total area for the MSA is 1,902.45 square miles. They are:
The San Juan-Caguas-Fajardo Combined Statistical Area (CSA) includes two metropolitan areas, one micropolitan area, and forty-five municipalities. A July 1, 2009 Census Bureau estimate placed the population at 2,732,036, a 4.16% increase over the 2000 census figure of 2,622,876. The San Juan-Caguas-Fajardo Combined Statistical Area comprises 68.9% of Puerto Rico's total population.
The San Juan metropolitan area, (in Spanish; área metropolitana de San Juan, abbreviated AMSJ), also referred to as the San Juan Metro Area is the area surrounding the City of San Juan which includes San Juan and its conurbation of the municipalities of Bayamón, Carolina, Cataño, Guaynabo and Trujillo Alto, and in some cases it also includes Toa Baja, this occurs in all possible directions (South, West and East, the North is bounded by the Atlantic Ocean), without constituting as a whole an administrative unit but are tied together economically. After the municipality of San Juan, together they are also the most populous municipalities in the commonwealth of Puerto Rico.
As per the 2015 United States Census Bureau estimates, the San Juan metropolitan area remains, by a significant margin, the most populous urban agglomeration in Puerto Rico with 1.25 million residents.