[1] Puerto Rico is the only U.S. territory whose data is recorded annually in American Community Survey estimates (as if it were a state) — the other U.S. territories have their data recorded only once every 10 years.
The U.S. Census Bureau counts the 78 municipalities of Puerto Rico as county-equivalents.
[3] Data for the municipalities of Puerto Rico is from the U.S. Census Bureau (2013-2017 American Community Survey 5-Year Estimates).
Most of the municipalities of Puerto Rico are among the lowest-income places in the United States.
Adjuntas, Puerto Rico has the lowest median household income of any county or county-equivalent in the United States.