From the 2000 Gale Encyclopedia of Multicultural America.
Encyclopedias etc. in print
Book of the States
Main floor, REF JK2403 .B6. 1940s to present. Allows one to compare the various states and territories. Includes Puerto Rico.
Hispanic Databook
Main floor reference collection (REF E184 .S75 H567) Detailed tables covering 23 different Hispanic groups, including Puerto Ricans.
Historical Statistics of the U.S.
Main floor, REF HA202 .H57. Historical stats colonial era to 2000. Does include some stats on Puerto Rico. Check the index in the back or go by subject.
Oxford Encyclopedia of Latinos and Latinas in the U.S. (v.3)
Main floor reference (REF E184 .S75 O97). Entries on Puerto Ricans in general, the independence movement etc.