The Atarazanas were the place where the ships were built in the medieval years. However, its use as a shipyard finished in the year 1503, so the ships that were built in the building had little relationship with America. It is a building from the 13th century, and due to its limited height, only galleys could be made, which were not appropiate for the trip to America and the defense of its cargo. Once the construction of larger ships was seen as necessary, these larger ships began to be made in the Aragonese and northern Spanish shipyards. So, the Atarazanas building started to be used as customs house, and as warehouses for oil, wool, and other miscellaneous products.

Since the Spanish arrival in America until the middle of the 16th century, numerous private ships left Seville and sailed to the Antilles first, and to the mainland later. This trade route was called the West Indies Race. Ships in this route could travel at any date and were often under attack by English corsairs. The so-called “loose ship” system marched unprotected, using caravels, naos and other low-tonnage ships, and at improper times and conditions, which caused many losses of ships and men.

One of the most significant examples of these kind of expedition was led by Pedro Menéndez de Avilés, who founded the first city in the United States, specifically in Florida, San Agustín. He planned his trip from the Atarazanas. In one of his travels from America to Seville he was caught not declaring part of the tax on the cargo of his ship, for which he was taken to the dungeons of the Atarazanas. During this time, he planned in this building the strategy for consolidating Spain’s position in North America, since the French planned to keep it, so he asked the king Felipe II to let him leave in exchange for carrying out these plans.

The ineffectiveness of the “loose ship” system led to its replacement by a more strictly regulated and protected commercial system. The Fleet and Galleon System started to be used in 1564. In this new system two fleets of galleons, artillery vessels, which were more robust and safe for transatlantic voyages, departed every year. The first of these fleets, known as “The Fleet”, departed in April, heavily armed for protection in case of attacks, with a final destination in Veracruz, Mexico.

The second, “Los Galeones”, left in August escorted by six or eight war galleons, ending in Nombre de Dios and Portobello, in Panama, with travels to Cartagena de Indias and other nearby ports. Previously, both fleets passed through Santo Domingo and Havana. In these ports they unloaded their European products, which were taken to Mexico City, Acapulco, Panama, El Callao and other ports in the American South Pacific. They spent the winter in those places and then in March they met in Havana to return together to Seville. From 1571 the so-called Manila Galleon was also organized, a commercial line that linked Acapulco with the Philippines.