The Spanish language developed from Vulgar Latin, with influences from Basque, and to some minor extent Celtiberian and Arabic, in the north of the Iberian Peninsula, between Biscay and current Cantabria's corners, partly as strongly innovative and differing variant from its nearest cousin, Leonese speech, with a higher degree of Basque influence.

Typical features of Spanish diachronical phonology include lenition (Latin vita, Spanish vida), palatalization (Latin annum, Spanish a�and Latin anellum, Spanish anillo) and diphthongation (stem-changing) of short e and o from Vulgar Latin (Latin terra, Spanish tierra; Latin novus, Spanish nuevo). Similar phenomena can be found in other Romance languages as well.

During the Reconquista, this northern dialect from Cantabria was carried south, and indeed is still a minority language in the northern coastal regions of Morocco.

The first Latin to Spanish grammar (Gram�ca de la Lengua Castellana) was written in Salamanca, Spain, in 1492 by Elio Antonio de Nebrija. When Isabel de Castilla was presented with the book, she asked, "What do I want a work like this for, if I already know the language?," to which he replied, "Your highness, the language is the instrument of the Empire."

From the 16th century onwards, the language was brought to the Americas and Spanish East Indies by Spanish colonization. Also in this epoch, Spanish became the main language of Politics and Art across the major part of Europe. In the 18th century, French took its place.

In the 20th century, Spanish was introduced in Equatorial Guinea and Western Sahara and parts of the United States, such as Spanish Harlem in New York City, that had not been part of the Spanish Empire.