House of Grimaldi
During the 11th century, Genoa tried several political systems in order to organize its city-state before leaders finally decided on the commune. The commune system gave power to the feudal families who settled the city so it was led by a committee of consuls who were chosen by those feudal families.
Grimaldo Canella was the son of Otto Canella, an early consul from a feudal family and the Consul of Genoa in 1162, 1170 and 1184. The Genoese Annals, which are the ancient manuscripts written in Latin, mention Grimaldo as Consul of Genoa but there's not much information about him and his early life. Grimaldo gave his patronymic name to his descendants and they became known as the Grimaldis.
The Grimaldi family came out of the Crusades as one of the four major ruling families of the Genoese urban nobility. The family was a mixture of ship owners, warriors and bankers. Grimaldo's grandsons and their children led maritime expeditions around the Mediterranean as well as the Black Sea, and they eventually went as far as the North Sea. The family became one of the most powerful families in Genoa.
Genoa developed an impressive commercial empire, which stretched west to the end of the Silk Road and spread across most of Europe. Genoese merchants travelled to Byzantium, Syria, London, Africa, China, London and the New World. They were relentless when it came to finding new business opportunities. They had regular sea routes, which stretched from the Black Sea to the North Sea and from Cyprus and Caffa to Antwerp and Bruges.
Genoa had few peers in the Mediterranean area and the leaders never missed an opportunity to enhance that position whenever possible. Genoa's sea power crushed the maritime ambitions of Pisa in 1284, and its fleet confronted the fleet of its rival, Venice, in four difficult wars. The sea battles were brutal as well as inconclusive.
As the years passed the Grimaldi family entered alliances with other feudal families to avoid a political coup that could destroy their power. When they entered an alliance with the Fieschi family the Guelphic Alliance was established, which meant the families supported the Pope and the Holy Roman Empire.
But the Grimaldis were banned from the city in 1271 and found refuge in Provence and in the castles of Liguria. They signed a treaty with the Court of Provence and the King of Naples to retake control of Genoa and in 1276 a peace treaty was signed, although it didn't end the civil war. Some members of the Grimaldi family stayed behind and raised their own armies. In 1299, factions of the family attacked the port of Genoa and then took refuge on the Western Riviera. The family entered different alliances at that time and their rivals, the Spinola family, was exiled thanks to Grimaldi tactics. At the same time the Grimaldis took the abandoned castles in Monaco, which were ideal locations from which to launch military and political operations against Genoa.
The fighting continued in Genoa in one way or another over the next century, but several of the old feudal branches of the Grimaldi family took advantage of the upheaval in Genoa and took possession of Monaco in 1395. The family ruled it as a condominium (when two or more sovereign powers agree to share equal dominium, without dividing it into national zones). That agreement is the origin of Monaco's principality today.
Before the agreement of 2002, a treaty between France and Monaco stated that if the reigning prince failed to leave a dynastic offspring their sovereignty would revert to France. The 2002 agreement expanded the pool of potential Grimaldi heirs to include dynastic collaterals of the reigning prince. In addition, Article 1 of Monaco's house law states that the reigning prince or princess must bear the surname of Grimaldi.