Because Puerto Ricans constitute a diaspora, it is difficult to locate them in terms of defined territory. Their "settlement" patterns include New York City and other major metropolitan areas off the islands, and the dispersed households of Puerto Ricans may include members living in as many as three to five locations on the islands and the mainland.
The main island of Puerto Rico is most densely populated along its coastal fringe. The four major metropolitan centers are San Juan, Ponce (south-central coast), Mayagüez (west-central coast), and Arecibo (north coast). The San Juan metropolitan area, which includes several cities and districts, extends in all directions except north (the seaward side). Old San Juan retains its prominent position at the mouth of San Juan harbor. Bayamón and Cataño ajoin the western limit of the metropolis. The business and financial center of Hato Rey, along the Rio Piedras, home of the main campus of the University of Puerto Rico, lie along the south end of the city, and the tourist districts stretch out along the ocean to the east.
Most of the settlements depart from the usual grid pattern of Spanish settlement and instead extend outward from town squares that might have once been centrally located. The development of public housing and land-annexation schemes to accommodate the growing population have undermined the centrality of town squares. Government housing-development schemes have been implemented islandwide.