The patron saint of Assisi isn’t St. Francis but San Rufino, the first bishop of the city; the cathedral is dedicated to him since the first half of the eleventh century.
Rufino died by being thrown into a river with a stone tied around his neck in the town of Costano. The body was transported to Assisi, precisely in the location where the Cathedral now stands, built by the faithful of Assisi and by the work of Giovanni da Gubbio. Dating to the XII century, it is the third built on the tomb of the martyr Bishop; the first was built in 412.
The date of the celebration of the Saint, since the XI century is on August 11th. In Assisi and in the diocese, the celebration of S. Rufino was moved to August 12th,as the 11th overlapped with the celebration for St. Clare.
St. Clare of Assisi, born in 1191 and died in 1253, is founder of the Poor Clares Mission, the first female order of the history of the Church. St. Francis had them dwell at San Damiano, where Clare remained until her death, giving rise to the first monastery of the Poor Clares. The basis of the Mission of St Clare is attributable to the concept of absolute poverty, i.e. the prohibition of every possession and the obligation to live in the alms. Clare was canonized in 1255. The celebration in honor of the Saint is celebrated on August 11th the day of her death. On the occasion of the her celebration, Assisi pays homage to her daughter with many festivities both liturgical and civil, besides, of course the Procession, a fair and fireworks. The feast has as its center the Church of St. Clare, where the body of the Saint rests.