The 1622, 1715, and 1733 flotas were an integral part of an economic system that had developed early in the three centuries of Spanish rule in the New World. A pattern of trade, controlled strictly by the Spanish crown, had evolved based on the mercantilistic policies of the day. Spain's policy was to establish a monopoly, keeping her colonies dependent on her. This monopoly was eventually challenged successfully by English and Dutch traders, but by law Spanish colonials could trade only with the authorized Spanish merchant flotas. As early as the 16th century a law was passed by the Casa de Contratacion, or "House of Trade," which called for the periodic sailing of fleets from Spain to the Caribbean twice a year (though they hardly ever sailed on schedule). The fleets carried manufactured goods for sale to the citizens of the New World, and were then filled with the rich treasures of the Americas for transport back to Spain.

The typical fleet consisted of several types of ships. Heavily armed galleons served as protection for the bulk of the fleet, merchant naos. The only difference between the nao and galleon was the amount of armament carried. Several pataches, small reconnaissance vessels, also accompanied the fleet, as well as resfuerzos or supply ships.. The fleet was led by the Capitana, or flagship, and the Almiranta, or vice-flagship.

The fleet would leave Spain (first from Seville and later Cadiz), sail down the coast of Africa until the reached the Cape Verde Islands. Here they sailed west with the prevailing tradewinds until they entered the Caribbean. At that point the ships split into two separate fleets, the Nueva Espana flota and the Tierra Firme flota (after 1648 it was called Los Galeones). The first fleet sailed to Mexico (Nueva Espana)'s port of Vera Cruz, while the second fleet visited the South American mainland ports of Cartagena, Nombe de Dios, and Porto Bello.

In these ports, the ships traded manufactured goods for the wealth of the Indies, such items as gold, silver, emeralds and other gemstones, hides, exotic woods, copper, tobacco, sugar, cochineal, indigo, and other valuables. In additions to these goods, another Spanish fleet called the Manila Galleons crossed the Pacific and sent treasures from the Orient to Acapulco and then to the Caribbean flotas. These commodities included such materials as ginger, cowrie shells, porcelains, silks, velvets, damasks, drugs, pearls, and ivory.

After a month or so of bartering at the trade fairs, the fleets were loaded for the return voyage. The two flotas rendezvoused at Havana for the voyage home to Spain. The ships were refitted and replenished and then the combined flota departed Cuba, sailing north to the Straits of Florida. When they reached the Gulf Stream, the ships were propelled past the Bahamas and eventually would set a course for the Azores and Spain.

The great flota system reached it height between 1590 and 1600. Then, over the next century the system began to slowly decline. Spain's leadership weakened and her debts increased, colonial mines produced less precious metals, privateer attacks increased, and other European powers began to colonize the Caribbean and break the Spanish trading monopoly. At the end of the 16th century, the average number of ships in the flota was 100; this was to degrade to 55 by 1610 and to 25 by 1640. At home, Spain suffered general economic and industrial decline and began to lose its shipbuilding industry, as attested to by the fact that by 1650 more than two thirds of the flota ships were of foreign construction. The Spanish navy was so weak by the end of the 17th century that often foreign warships (usually belonging to the nation that Spain owed the most money to) escorted the flota home. The loss of the 1715 and 1733 treasure flotas were a tremendous blow to Spain in the early 18th century. Finally, the last flota to make the transatlantic run sailed in 1778, and Spain officially declared free trade among its colonies.

• Go to the 1622 Spanish Treasure Fleet page.
• Go to the 1733 Spanish Treasure Fleet page.