Puerto Rico is neither a state nor a country, so it is difficult to declare a "statehood" or "independence" day. For her Celebrating the States blog -- an elaborate, year-long celebration of statehood anniversaries -- my wife Pam (librarian and honorary geographer) has chosen March 2. Read her post for an explanation of that choice and a very good explanation of Puerto Rico's status, along with a discussion of our personal connection to the island through our late dog, Clover.
Read my addition in the Comments section. It is no coincidence that the project I did in Puerto Rico (without ever visiting) was for a shampoo factory. More specifically, it was for medicinal, delousing shampoo. Tax incentives meant to stimulate the Puerto Rican economy have made Puerto Rico an important enclave for Big Pharma. Research and development done in the 50 states (a lot of it in New Jersey, as was the case with our client) while the manufacturing is done in Puerto Rico.