Campo Maior, is a municipality in the Portalegre District, Alentejo Region, Portugal.
Campo Maior was certainly a Roman settling - the ancient Muro Dam is close by - which went under control of the Moors for half a millennium. In 1219, it was conquered by Christian knights, the Pérez de Badajoz family, who then gave the village, which belonged to the municipality of Badajoz, to the Church of Santa Maria do Castelo (Saint Mary of the Castle).
On May 31, 1255, King Alfonso X of Castile promotes the village to town status.
In 1260, Bishop Friar Pedro Pérez, the Town Lord, grants the first charter (foral) to the inhabitants of Campo Maior. He also introduced the town´s first coat-of-arms, showing Our Lady and a lamb, with a legend "Sigillum Capituli Pacensis".
On May 31, 1297, the Treaty of Alcanizes was signed by King Ferdinand IV of Castile and King Denis of Portugal, whereby Campo Maior, together with Olivença and Ouguela, were transferred to Portugal.
The Castle east of the village was rebuilt by King Denis in 1310. In the 17th and 18th Centuries, other fortifications were built and Campo Maior became an important garrison town.
King John II (1481–1495) granted a new coat-of-arms to Campo Maior: a white shield, with the Arms of Portugal on one side, and John the Baptist, patron saint of the town, on the other side.
In 1512, King Manuel I renews the charter (foral) of Campo Maior.
From the late 15th Century, many of those persecuted by the Inquisition in Castile took refuge in Portugal. Part of them settled in Campo Maior, which saw its population increase substantially. As a consequence, in the 16th Century, the town´s New Christian community was so numerous that it provided most of the accused of Judaism which were included in the Portuguese Inquisition´s Auto-de-fé that took place in nearby Évora.
The war with Castile from 1640 brought big changes. The need to re-fortify the town, which had grown markedly outside the medieval perimeter during the previous three centuries, and the urgency to build a new fortified perimeter to defend the inhabitants of the "new town" from the incursions of the Castilian armies, were the reasons that forced the Kings of Portugal to invest large amounts of money, and to send contingents of military engineers, specialized workers and even more non-specialized workers. The garrison had then a substantial size. It is estimated that, in late 17th Century, one out of four inhabitants of Campo Maior was military. Campo Maior was also the main home of the mercenary Dutch troops that fought in Alentejo. The town was at that time the second most important garrison in Alentejo, after Elvas.
In 1712, during the Spanish War of Succession, the Castle of Campo Maior was besieged by the Spanish Army, commanded by the French Alexandre Maître, Marquis de Bay. For 36 days, he launched tons of projectiles on the town and managed to breach one of the bastions. However, upon crossing the breach, the Spanish Army suffered heavy casualties and retreated in defeat.
The early 19th century were agitated in Campo Maior: a siege in 1801 by the Spanish during the War of the Oranges, and a local rebellion in 1808 against the French who were then engaged in the Peninsular War.
In 1811, a new Napoleonic invasion besieges the town for one month until capitulation. But that gave time for the Anglo-Portuguese Army, under the command of British General Beresford, to arrive and disband the French. The town then earned the title of Vila Leal e Valorosa (Loyal and Valorous Town), now inscribed in its coat-of-arms.