Spanish is spoken by more than 400 million people around the world, and it is the primary language of 332 million people (Spanish language, 2004). It is the official language of almost all of Latin America and of Spain. It is also widely spoken in the U.S., Canada, and the Philippines. In the United States alone, there are 39 million people of Hispanic origin (Grow, 2004, p. 60) (many of whom call themselves Latinos) and 78% of them speak Spanish (Grow, 2004, p. 62).
Modern Spanish originates with Vulgar Latin, that is, Classical Latin modified by the various autochthonous languages of the Iberian Peninsula. In the 8th century AD, the Moorish conquest of Spain infused Vulgar Latin with Arabic words. During the 13th century, due to the political domination of the Kingdom of Castile over other regions, and thanks to the efforts of king Alfonso X--the dialect of Castile, known as Castilian (castellano) spread across Spain. In the 15th century, the Moors were expelled from the Peninsula, and Castilian was declared the official language of Spain. The eight century long occupation by the Moors resulted in the incorporation of over 4000 words of Arabic origin, making Arabic the second most important linguistic influence on Spanish after Latin (Lapesa, 1980, p. 133). In the south of the country, the Andalusian dialect coexisted with Castilian. Starting in 1492, the expedition ships destined to the New World departed from the southern ports, and most of the crew members hailed from the south as well. Therefore, both Castilian and Andalusian were exported to the Americas.
Gradually, words from the autochthonous peoples of the Americas became part of the vocabulary of the Spanish speakers on this side of the Atlantic. This is why Latin American Spanish differs somewhat from European Spanish.
Spain lost all of its American colonies between 1810 and 1825 (with the exception of Cuba, Puerto Rico, and the Philippines), but the legacy of the language remained. Nowadays, Spanish is the official language of nineteen nations in North, Central, and South America.
"Spanish Language & History," ALS International, 31 January 2004
Grow, Brian. "Hispanic Nation." Business Week 15 March 2004: 59-70.
Lapesa, Rafael. Historia de la lengua española. 9th ed. Madrid: Gredos, 1980.