During the era of the Catholic Kingdoms of Spain during the Middle Ages, Spain was broken into many kingdoms, so Spain did not have a common flag. However, many of the kingdoms used red and yellow in their coat of arms, as a set of common colours.
However, the Standard of Aragon was 4 red stripes with 5 yellow. Almost a precursor to the current flag, and directly linked with the current flag of Catalonia.
However, with the marriage of Joanna of Castile and Philip, the Archduke of Austria (Philip I of Castile), the Cross of Burgundy entered into the list of Spanish flags. Slowly, over time, with mergers and takovers, it became the flag of Spain, and the first flag to be flown in the New World. The Cross of Burgundy is a diagonal cross of red on white, with the red arms being knotted.
However, it was Charles III, in 1785, who brought in a new set of flags. Up until then, the Spanish flag had been similar to many others in Europe, being the coat of arms on white. It was felt that on the battlefield, this caused a lot of confusion.
So, a new tribranded flag was introduced. It featured the common colours of red and yellow. Both being associated with Spain, and being very visible on the battlefield. The flag featured red stripes top and bottom, and a central yellow stripe that was twice the width of the red stripes. It was charged with a simplified version of the coat of arms towards the hoist in the central yellow stripe.
At sea, Spain had a naval flag which featured 5 stripes of yellow, red, yellow, red, and yellow. This was modelled from the Coat of Arms for the Kingdom of Aragon, and from the flag of Catalonia.
The flag of Catalonia follows the same pattern, but features 9 stripes.
During 1873, King Amadeo I abdicated, which led to the formation of the First Spanish Republic. A new tricolour was debated, however, it was decided to be much faster, and simpler, to simply cut the crown off the flag, and patch the flag with a piece of yellow cloth!
The Republic lasted until Brigadier Martinez Campos announced his support for Alfonso XII, the following year. Since the army refused to act against them, the government effectively collapsed.
In 1931, the monarchy was overthrown again, and the second republic was born. This time, they scrapped many of the monarchistic emblems, as well as the flag. The new flag was a red, yellow, and indigo tricolour. The stripes where all the same width, and the use of indigo was supposed to represent Castile. And a new coat of arms was introduced, being placed in the centre of the flag. This coat of arms will crop up later...
Franco then became the fascist dictator of Spain until 1977. He saw the return of the old red and yellow flag, however, it was charged with the Eagle of St John, and supporting a shield made up of the coats of arms from the old Catholic monarchs.
With Franco's death, and the comeback of the monarchy, the flag was altered. Though not by a lot. Essentially, the flag was kept the same, but the wings of the eagle where spread a little wider.
Then, with the new constitution of 1981, the current flag was introduced. This featuring the current national coat of arms placed towards the hoist of the flag. It is worth noting that the coat of arms has no text, meaning that the Spanish, when they fly the flag, allow the coat of arms to be reversed!
Spain also uses a simplified version of the flag.
Very common to see being used by the people of Spain is a simplified flag, which does not feature the coat of arms.Can be seen on homes, cars, and at football stadiums!