210px-Mona_Island_LightPyra­mi­dal skele­tal cast iron tow­er with cen­tral cylin­der, lantern and gallery. Orig­i­nal­ly paint­ed black, the light­house is now cov­ered with rust. The active light  is on a 40 ft  steel tow­er.  The light­house has dete­ri­o­rat­ed severe­ly since deac­ti­va­tion and is in dan­ger of being lost.  The aban­doned light­house has been added to the Light­house Digest Dooms­day List.  The tow­er is “beyond repair.” The orig­i­nal 2nd order Fres­nel lens, the largest lens ever used in Puer­to Rico,  is in stor­age for even­tu­al dis­play at a pro­posed research and vis­i­tor cen­ter on the island. The Isla de Mona, part of the Com­mon­wealth of Puer­to Rico, is locat­ed in the Mona Pas­sage between the Puer­to Rican main­land and the Domini­can Repub­lic.

The Mona light­house entered ser­vice on April 30, 1900. It was con­struct­ed at the high­est point of the island, near its east­ern end, to guide nav­i­ga­tion through the busy but dan­ger­ous Mona Pas­sage. Rafael Rave­na pre­pared two very dif­fer­ent plans, one for a tra­di­tion­al mason­ry build­ing with a cen­tral court­yard and twen­ty-five rooms, which would have been the most majes­tic light­house in the Caribbean, and the oth­er for an iron tow­er flanked by two wood and met­al build­ings 64 feet long by 50 feet wide. Both designs would house three keep­ers.

The sec­ond option was cho­sen in Novem­ber 1885 due of its low­er cost, faster con­struc­tion, and the sus­pi­cion that Mona’s porous sub­strate would not ade­quate­ly sup­port a large stone and brick build­ing. The dif­fi­cul­ty of trans­port­ing mate­ri­als to Mona and oth­er obsta­cles delayed con­struc­tion so that at the end of the Span­ish-Amer­i­can War only part of the mate­r­i­al was onsite. The U.S. gov­ern­ment obtained the remain­ing mate­r­i­al and fin­ished the project with a sin­gle res­i­dence. Although it is fre­quent­ly stat­ed that the tow­er was designed by Gus­tave Eif­fel, which is pos­si­ble because Eif­fel designed a large vari­ety of struc­tures, no men­tion is made of the fact in Ben­jamin Nistal-Moret’s study nor in the well-doc­u­ment­ed work Faros Españoles de Ultra­mar.

The Mona light­house had the only sec­ond-order lens used in Puer­to Rico, which pro­ject­ed its light 22 miles away; this lens is in Mona, dis­as­sem­bled and under the cus­tody of the Depart­ment of Nat­ur­al and Envi­ron­men­tal Resources, which will dis­play it in Mona’s future Cen­ter for Research and Vis­i­tors. The light was elec­tri­fied in 1938 and auto­mat­ed in 1973. The build­ing was final­ly aban­doned in 1976 and since then the tow­er has dete­ri­o­rat­ed to the point of being beyond repair. Giv­en its poor con­di­tion and remote loca­tion, it is like­ly that this light­house will nev­er be restored.