Legend says that Siena was founded by Senio and Ascanio, sons of Remus, of the famous duo Romulus and Remus who founded Rome. Statues of the wolf feeding the twins are spotted throughout Siena, but without historical foundation! Instead, the Romans established a military outpost in 30AD called Siena, and it developed into a busy little trading post in the following years.
The Lombards arrived in 6th century AD, and the Franks also had an input in the governing of the city. Great works were carried out, the most important being the Via Francigena, the road which linked Rome to France, used by pilgrims and travellers; this greatly increased Siena's importance. During this time the Church was actively involved in governing the city, especially between the 9th and 11th centuries, after which the Sienese people claimed their right to govern and administer the city.
Economic and military power grew enormously and inevitably friction grew between Siena and Florence, as both cities tried to enlarge their territory. There were many battles between the two cities between the 13th and 15th centuries, some won by Siena, but eventually Florence had the upper hand and Siena was incorporated into Florentine territory and administration.
Despite both external disputes with neighbours and internal disputes over government, in the years 1150-1300 great artists were discovered and the city was adorned with beautiful monuments such as the Duomo, the Palazzo Pubblico and the Torre del Mangia. The Council of Nine, a beneficient governing body in the mid-13th century, were behind a lot of these improvements, which you can still see today. However a devastating plague hit Siena in 1348, while the citizens were planning the extension of the Duomo, and killed 3/5 of the population, after which the city was slow to recover.
With a diverse group of rulers from the 14th -19th centuries, including Emperor Charles V and Cosimo I de' Medici, Siena grew in economic power, with the famous bank Monte dei Paschi di Siena giving employment and security to the citizens throughout the ages. When Italy formed a republic, Siena became part of the region of Tuscany and prospers today from a combination of finance and tourism, thanks to its beautiful artistic heritage.