One of the former kingdoms of Spain, Aragón was initially a Frankish feudal county (Jaca), before becoming a self-proclaimed kingdom, which was united to the kingdom of Pamplona (later Navarre) in 925. Later split from the kingdom of Navarre, the kingdom of Aragón was re-established in 1035 and lasted through period. The city of Zaragoza was conquered from the Moors in 1118, to become the capital.
Among the other Spanish territories of the time, the County of Barcelona was a particularly powerful rival of Aragon's, ruling Valencia, the Balearics and parts of modern France. But, because of the dynastic union of a Count of Barcelona (Ramon Berenguer IV) with a Queen of Aragón (Petronila), with their son inheriting all their respective territories, Aragón became the name of the joint crown, although the two components maintained cultural separations.
This Crown was effectively disbanded after the dynastic union with Castile in 1479, when Ferdinand V of Aragon married Isabella of Castile (Their daughter, Catherine of Aragon, was to be the ill-fated bride of Henry VIII of England, after the early death of his brother, Prince Arthur). It was under Ferdinand and Isabella that the last of the Moors were expelled from Granada, and this exodus of Muslims and Jews left the peninusla to the Catholics.
The Kings of Aragón (called by some present-day historians "Catalan Kings of Aragón", "Catalan Kings", "Count-Kings", or "Counts of Barcelona and Kings of Aragón" so that the role played by Catalonia in the crown is not ignored inadvertently) ruled territories that consisted of not only the present administrative region of Aragón but also Catalonia, and later the Balearic Islands, Valencia, Sicily, Naples and Sardinia.
The King of Aragón was the direct King of the Aragonese region, and held also the title of King of Valencia, King of Mallorca (for a time), Count of Barcelona, Lord of Montpellier, and, only temporally, Duke of Athens and Neopatria. Each of these titles gave him sovereignty over a certain region, and these titles changed as he lost and won territories.
The real centre of this kingdom was Barcelona, since it had a seaport and was near the geographical centre of the Crown of Aragon, while Valencia was the most important seaport for trade until approximately the 18th century. Present-day historians usually call the Crown the "Crown of Aragón", the "Catalan-Aragonese Confederation" or simply "Catalonia-Aragón", many times depending on whether that historian lives in Aragón or in Catalonia. The Kingdom of Aragón is called simply Kingdom of Aragón. Saying just "Aragón" is ambiguous and should be avoided. Barcelona was the center of what was in many ways a Mediterranean Empire, ruling the Mediterranean Sea and setting rules for the entire sea (for instance, in the Libre del Consolat del Mar, in Catalan).
The contents of this page was originally largely taken from the Wikipedia text, with some expansion