Despite the formation of roads in the valley bottom of the Via Francigena during the twelfth century, the village was still a popular hospitality stop for travelers. Additionally, the town continued to expand due to the development of commercial traffic between Pisa and Siena, and the desire to avoid the territories controlled by Florence. The easy communications with the marine Republic, where the merchants from San Gimignano had their own anchorage, allowed them to start up economical relations, especially in the Mediterranean and with Northern Europe. In step with the territorial and mercantile expansion of San Gimignano, there was also a corresponding development of the village, which officially became a "town", with the building of the second ring of walls in 1207.
With its involvement in the anti-Siena campaign in the middle of the thirteenth century, Florence began trying to lay its hands on the village, and it finally obtained its subjugation, sealed by a pact in 1353, after which it erected a new fortress on the hills of Montestaffoli. From that time onwards San Gimignano was subjected to Florentine domination, first under the government of the Republic, and later under the rule of the Medici family.