[8] Mona, along with Puerto Rico, Vieques and Culebra, were ceded to United States from Spain in 1898 under the Treaty of Paris.

It was designated a nature reserve in 1986, and BirdLife International and the Puerto Rican Ornithological Society recognized it as an Important Bird Area in 2004.

[13] Mona and Monito are home to a number of unique animal and plant species found nowhere else in the world.

[16] Mona is home to the largest population of the rare and Critically Endangered[17] Puerto Rico applecactus or higo chumbo (Harrisia portoricensis).

Its numbers have greatly decreased due to the presence of invasive species such as cats which predate on the young, and boar which threaten their nesting sites.

[21][22] Mona represents the largest nesting site for hawksbill sea turtles (Eretmochelys imbricata) in the Caribbean.

[3] The most common form of transportation is by private yacht, though commercial excursions are available from Cabo Rojo for small groups.