Sugar plantations and their processing plants proliferated from the 15th century throughout the tropics for the production of refined sugar.
For many years, the producers had no use for the by-product of sugar production called molasses, which would overflow from the pots used to cure the sugar.
Once harvested, sugar canes are crushed, and the sap is cleared from impurities by boiling and taking skimmings off the top. These skimmings when fermented with molasses produced rum.
By the 17th century, many sugar works installed copper pot stills to produce their own rum, later attracting the custom of the British Royal Navy, adopting it as their daily ration on board their war ships, as it lasted in the casks for longer than water or beer, and kept the sailors drunk enough to be subdued and blind them to the squalors they endured. In 1731 Sailors were permitted a staggering half pint of rum and a gallon of beer 'should' they want it!
Daily rations reduced greatly until the 31 July 1970, known as 'Black Tot Day', when the daily ration of Pussers Rum came to an end, but the legends of the bygone Admirals who sailed the tropics and played such a large part in establishing rum live on. In 1655 Admiral Penn captured Jamaica from the Spanish and established the first rations. In 1740 Admiral Edward Vernon reduced the ration to have a 'quart of water for every pint of rum' which took on the name of 'Grog', named after Vernon's grogram Naval Cloak, it's weaker, unpleasant taste was overcome with the addition of sugar and lime, called a limey, and us British are still called Limeys to this day.
As sugar plantations spread throughout the tropics, so developed today's different regional styles of rum. The British colonies with their darker Naval styles, the French-speaking islands produce their own agricole rums, distilling the sugar cane juice, not the molasses, producing a more assertive rum, often aged for greater depth, smoothness and character. And the Spanish style, light bodied rums from Puerto Rico, Cuba and the Virgin Islands are made primarily in a column still, and get little if any barrel ageing.