Introduction: The Bourbons, a new dynasty in Spain

The Habsburg dynasty finished in 1700 with the death of Charles II, who had appointed as his heir the french prince Philip of Bourbon, while Archduke Charles of Habsburg (Austria) claimed his rights to the throne. However, this led to an international conflict as the balance of power was disturbed and inside Spain the territories supported different pretenders. This led to the War of the Spanish Succession (1701-1714).
Philip V of Bourbon won the war. He instituted the french absolutist and central system, starting the territorial unification of the crowns of Aragón and Castile, sharing new laws and establishing an identical administration with uniform institutions through the Nueva Planta Decrees imposing the Castilian system. The reigns of Philip V and Ferdinand VI followed the french absolutist and central system.
Characteristics of the Liberalism in Spain: A Liberal Revolution during two wars
The first attempt to establish a constitutional system in Spain took place during the War of Independence (also known as the Peninsular War). In opposition to the crowning of Napoleon’s brother juntas were created. They met in the Cádiz Cortes and drafted the first Spanish Constitution (1812). The second and final attempt took place during the First Carlist War, a civil war between 1833 and 1839, in which Carlist absolutists fought against liberals supported by Isabella II. Thus, the implementation of the liberal system in Spain will be affected by both military conflicts. As a result, the spanish liberalism will develop important problems in its political system: 
1- The monarchy was politically active and nearly always in favour of the moderates.
2- Members of the nobility, military and clergy formed political cliques and used their influence for personal gain (camarillismo).
3- Census suffrage gave only 1% of the population the right to vote and election results were systematically manipulated in favour of the party in power (electoral fraud).
4- Families with political and economic power could decide on political candidates. They could also corrupt election results (caciquismo).
5- The army: an arbitrator. The limitations of the electoral system and electoral fraud often caused the opposition party to start military revolts (pronunciamientos) to force the monarch to hand over control of the government. The National Militia and revolutionary civilian groups took part in these revolts.
6- Weak constitutions: The different liberal groups wanted their political models to be reflected in the Constitution creating 7 texts in 64 years.

Ferdinand VII: the restoration of absolutism
Ferdinand started the age of Six years of absolutism (1814-1820) abolishing all reforms and persecuting liberals. The pronunciamientos against him achieved a liberal age in the Liberal Triennium (1820-1823) with Coronel Rafael de Riego, but they were defeated by the Holy Alliance with the help of the One Hundred Thousand Sons of St. Louis. Absolutism came back with the Ominous Decade (1823-1833), showing the structural problems of the Ancien Régime with political and economic problems. The king would turn his position with the birth of his daughter Isabella: the Salic Law from the Bourbon family didn’t allow her to be the queen, so he approved the Pragmatic Sanction (1830), impeding Charles, his absolutist brother, to be king.

Regency of Maria Christine (1833-1840) & the First Carlist War
Charles and his supporters initiated an uprising in the First Carlist War (1833-1839), mostly in rural and conservative areas and finishing with the Convenio de Vergara. Maria Christine, as a regent, needed the support of the moderate liberals so she gave them the political power in exchange. The Mutiny of La Granja made progressives to enter the government with Mendizábal. He began the abolishment of the Ancien Régime by introducing fiscal reform, dissolving manorialism, and through the disentailment of property and the confiscation of Church property. The payment of tithes, the Mesta, internal custom duties and guilds were also abolished. The Constitution of 1837 was approved, with a slightly open census and some rights.
Regency of Espartero (1840-1843)
In 1837, moderate liberals with increasingly conservative policies took control of the government. Maria Christina was forced to step down, liberals took power with General Espartero. He continued with reforms over trade, but those liberalist actions bothered Catalonia’s industry and the excessive authority he imposed got him away from the government.
The Moderate Decade (1843-1854)
During almost the entire reign of Isabella II as an adult, Spain’s Moderate Liberal Party, led by General Narváez, remained in power. The new Cortes adopted a moderate constitution (1845). State and municipal administration was reorganised, and only the Basque Country and Navarre held on to their statutory laws. The moderate liberals also adopted measures to centralise taxes, create a penal code (1848) and develop a national education system. In 1851, the state signed the Concordat with the Holy See. The authoritarian tendencies of political leaders like Narváez and Bravo Murillo, the influence of the political cliques (camarillas) and electoral fraud caused another progressive military revolt.
The Progressive Biennium (1854-1856) & the decline of the system (1868)
Espartero took over the government again and focused on economic reforms:
The confiscation of commons and municipal property (Confiscations of Madoz, 1855).
The General Railway Law and the Mining Act to boost the railway system and the mining industry, although they were financed by foreign capital.
In 1856, the Liberal Union got the power and O’Donnell and Narváez from the Moderate Party alternated in power practising a colonial policy, while the country started a democratic and republican small movement.
The Revolution and the provisional government (1868-1869)
The economic crisis (US Civil War, Railway and financial crisis) , the monopoly of the moderates in the government and the new ideas in society created a revolution in 1868 with the union of progressives, democrats and unionists, led by Prim. They won the conflict and Isabella was thrown into exile with her son Alfonso. They formed a provisional government and created the democratic Constitution of 1869.

The monarchy of Amadeo I (1870-1873)
Amadeo of Savoy was chosen king of Spain, but Prim was killed at his arrival and found Spain sunk in conflicts (Second Carlist War, Cuban insurrection, conflicts in the political parties). He abdicated in 1873.
The First Republic (1873-1874)
Republic was the only option in a country without a monarch, and the instability of the government caused four different presidents (Figueras, Pi i Margall, Salmerón, Castelar) who had to deal with the divisions in the government, the Cuban insurrection, the Second Carlist War, social protests, the Cantón of Cartagena that led into a new monarchy based on the alfonsinos.