October 4 has a special significance to Real de Catorce as thousands of pilgrims come to the village to pay homage to the patron saint, Saint Francis of Assisi. The religious festival includes processions, indigenous dances and music in which the pilgrims begin arriving in late September and sometimes stay until mid-October. The village is so crowded that there are not enough restrooms for the tens of thousands of people. Many local residents and business people close their homes and shops and leave town during the celebration.

The Parish Church has a statue of Saint Francis of Assisi on a side alter. The neo-gothic alter was constructed in the late 1800s. The statue is wood and is jointed at the arms and legs so that the statue can be moved and even made to stand. The statue was originally in the old church by the cemetery, but when the locals noticed that the paint was chipping away from his feet (presumably from his late night wanderings looking for souls to save) they moved him closer to the center of town, placing him on a side alter in the Parish Church.

While there is a constant stream of individuals visiting the shrine, October 4 is the day of the main celebration as this is the Feast Day of Saint Francis of Assis. In the room just to the left and rear of the church one can find hundreds of hand painted plaques, adorning the walls. These “retablos” are left by the faithful to give thanks to the saint for having performed a miracle in their life.

Saint Francis of Assisi (September 26, 1181 – October 3, 1226) was a Roman Catholic friar and the founder of the Order of Friars Minor, more commonly known as the Franciscans.

Saint Francis is known as the patron saint of animals, birds, and the environment, and it is customary for Catholic churches to hold ceremonies honoring animals around his feast day of October 4.

Saint Francis was born to Pietro di Bernardone, a prominent businessman, and his wife Pica Bourlemont, about whom little is known except that she was originally from France. He was one of seven children. Pietro was in France on business when Francis was born, and Pica had him baptized as Giovanni di Bernardone in honor of Saint John the Baptist, in the hope he would grow to be a great religious leader. When his father returned to Assisi, he was furious about this, as he did not want his son to be a man of the Church. Pietro decided to call him Francesco (Francis), in honor of the child's maternal heritage.

Legend has it that St Francis thanked his donkey at his bedside for carrying and helping him throughout his life, and his donkey wept.