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In 1519 he led an expedition from Santiago (today's Jamaica) with the intent to map an area from the Yucatan Peninsula to the Panuco River, near present-day Tampico, Mexico. During his voyage to Mexico, he followed the Gulf coastline from Florida, stopping at a large river on June 2, 1519, where he observed over forty Native American villages. He named the river Espíritu Santo, which early historians assumed was the Mississippi but more recently is believed to have been Mobile Bay and the Alabama River. On June 24th, he stopped to explore another large bay and river, naming it Corpus Christi Bay.
One of the very first known maps of Texas and the Gulf Coast region was drawn by the Spanish explorer and cartographer, Alonso Álvarez de Pineda.
When he finally arrived at the Panuco River (Las Palmas), he spent over 40 days making ship repairs and working on a map of his Gulf Coast transit. Tragically, de Pineda was killed in a battle with Huastec Indians at the Panuco River, but his map made it back to the Governor of Santiago and then to Spain. This rather crude map was important for its establishment of Spain's North American coastal boundaries, verification that Florida was a peninsula rather than an island and invalidated the belief in a sea passage to Asia through the Gulf. The original map is now stored at the Archivo General de Indias in Seville, Spain.