The current flag of Puerto Rico was officially adopted in 1922.
The flag is similar to the flag of Cuba, as both were designed at the same time. The red stripes are symbolic of the "blood" that nourishes the three branches of its government; Legislative, Executive and Judiciary.
The white stripes represent individual liberty and the rights that keep the government in balance. The blue triangle stands for the "Republican Government", represented by the three branches, and the white Lone Star represents "The Commonwealth of Puerto Rico."