By the Middle Ages, the county of Portugal had developed around Porto. In 1095, Teresa of Leon, the daughter of Castilian King Alfonso VI, married Henry of Burgundy and bought Portugal as a dowry. Control over this territory was a matter of great dispute between Muslims and Christians during the Reconquest, which lasted for almost eight centuries.
 
Porto had acquired the city walls in Roman times. They were reconstructed in the 12th Century, when Bishop Hugo took control of the county and granted it a charter. The wall was redesigned in the 14th Century. It surrounded the hills of Vitoria and Se and extended in the direction of the river, where the Royal Customs House was located.
 
Following the Reconquest, Portugal became an independent kingdom. Gradually it expanded to its current frontiers, as it had taken back territory from the Moors at the turn of the Millennium under the rule of King Dom Afonso.

The King of Portugal and Philippa, Joao I, and the daughter of the Duke of Lancaster married in Porto in 1387. This marriage was meant as a symbol of the alliance between Portugal and England, the oldest military alliance in the world, recognised by NATO. King Joao I stayed in the Church of St Francis at the time of his marriage, a testimony of his esteem for the Franciscan order. As a UNESCO World Heritage Site, this church, located in the old town, is widely considered the most important Gothic building in Porto today, showcasing extraordinary Baroque interiors. Other monuments dating back to this time, include the Medieval Tower, Town Hall, the Primitive Wall and the Beco dos Redemoinhos House.