Clare was born on 16th July, 1194,  and her youngest sister Agnes was born in 1197 or 1198. Their father was Favarone Scifi, Count of Sasso-Rosso, the wealthy representative of an ancient Roman family, who owned a large palace in Assisi, near St.Rufino's cathedral,  and a castle on Mount Subasio, near Assisi.  Their saintly mother, Blessed Hortulana, belonged to the noble family of the Fiumi and was conspicuous for her zeal and piety.  Their cousins Sylvester and Rufino were both priests and joined St.Francis in 1209 and 1210.

She sought him out secretly and she confided to him her desire to live "after the manner of the holy Gospel", begging him to help her.  Francis, who at once recognized in Clare one of those chosen souls destined by God for great things, promised to assist her.
On Palm Sunday, 18th March, 1212,  Clare, arrayed in all her finery, attended high Mass at the cathedral, but when the others pressed forward to the altar-rail to receive a branch of palm, she remained in her place as if rapt in a dream. The bishop descended from the sanctuary and placed the palm in her hand.
On the night of the same day she secretly left her father's house and proceeded to the humble chapel of the Porziuncola, where Francis and his disciples met her with lights in their hands. Clare then laid aside her rich dress, and Francis, having cut off her hair, clothed her in a rough tunic and a thick veil.
She was placed by Francis provisionally with the Benedictine nuns of San Paolo, near Bastia, but her father, who had expected her to make a splendid marriage, and who was furious at her secret flight, on discovering her retreat, did his utmost to dissuade Clare from her heroic proposals, and even tried to drag her home by force. But Clare held her own with a firmness above her years, and Count Favarone was finally obliged to leave her in peace. A few days later Francis, in order to secure Clare the greater solitude she desired, transferred her to Sant'Angelo di Panzo, another monastery of the Benedictine nuns on one of the flanks of Subasio.

Sixteen days later Agnes repaired to the same convent, determined to follow her eldest sister's life of poverty and penance,  At this step the fury of Count Favarone knew no bounds. He sent his brother Monaldo, with several relatives and some armed followers, to St. Angelo to force Agnes, if persuasion failed, to return home.

Monaldo, beside himself with rage, drew his sword to strike the young girl, but was temporarily paralyzed:  his arm dropped, withered and useless, by his side; others dragged Agnes out of the monastery by the hair, striking her, and even kicking her repeatedly. Presently Clare came to the rescue, and of a sudden Agnes's body became so heavy that the soldiers having tried in vain to carry her off, dropped her, half dead, in a field near the monastery. Overcome by a spiritual power against which physical force availed not, Agnes's relatives were obliged to withdraw and to allow her to remain with Clare. St. Francis, who was overjoyed at Agnes's heroic resistance to the entreaties and threats of her pursuers, presently cut off her hair and gave her the habit of Poverty.

Francis obtained "San Damiano" from the Benedictines as a permanent abode for his spiritual daughters.  It was a small rude dwelling adjoining the humble chapel, which he had helped to rebuild with his own hands.  Clare's and Agnes' mother Hortulana, their sister Beatrice, and several other women of Assisi joined Clare and Agnes. Thus began the Order of the Poor Ladies, or of Poor Clares, as this Second Order of St. Francis came to be called.  In the beginning, they had no written rule to follow beyond a very short formula vitae given them by Francis.

In 1215, Clare, against her will, was appointed abbess of the convent and occupied this position for 40 years.  until Her death. In 1219 a group of Benedictine nuns in Monticelli,  near Florence, asked to become Poor Clares and Francis assigned Agnes as their abbess.  A letter written by her to Clare after this separation is still extant, touchingly beautiful in its simplicity and affection.

In the same year, while Francis was in the East, Cardinal Ugolino, then protector of the Order, drew up a written rule for the Poor Clares at Monticelli, taking as a basis the Rule of St. Benedict. This new rule took away from the Poor Ladies the Franciscan character of absolute poverty  and made them for all practical purposes a congregation of Benedictines.  It was approved by Pope Honorius III (Bull, "Sacrosancta", 9th Dec., 1219).

Clare found that the new rule allowed the holding of property in common, therefore she courageously and successfully resisted the innovations of Ugolino.  
Francis had forbidden the Poor Ladies, just as he had forbidden his friars, to possess any worldly goods even in common. Owning nothing, they were to depend entirety upon what the Friars Minor could beg for them.

Full of zeal for the spread of the Order, Agnes established from Monticelli several monasteries of the Poor Ladies in the north of Italy, including those of Mantua, Venice, and Padua, all of which observed the same fidelity to the teaching of Francis and Clare, depending solely on alms, forced to have complete faith on God to provide through people; a lack of land-based revenues was a new idea at the time.   Nothing perhaps in her character is more striking and attractive than her loving fidelity to her eldest sister's ideals and her undying loyalty in supporting her struggle for Seraphic Poverty.

Clare loved music and well-composed sermons. She daily meditated on the Passion. When she learned of the Franciscan martyrs in Morrocco in 1221, she tried to go there to give her own life for God, but was restrained. It was to her Francis turned when in doubt, and it was she who urged him to continue his mission to the people at a time when he thought his vocation lay rather in a life of contemplation.  
Brave and cheerful to the last, in spite of her long and painful infirmities, she caused herself to be raised in bed and she made more than one hundred corporals, for all the churches in the plain and on the mountains of Assisi.
Toward the end of her life, when the was too ill to attend Mass, an image of the service would display on the wall of her cell; thus her patronage of television.

When in an attack of blindness and illness, St. Francis came for the last time to visit San Damiano, Clare erected a little wattle hut for him in an olive grove close to the monastery, and it was here that he composed his glorious "Canticle of the Sun".
In 1226, after St. Francis's death the procession which accompanied his remains from the Porziuncola to the town stopped on the way at San Damiano in order that Clare and her daughters might see him for the last time.  So far as Clare was concerned, Francis was always living, and nothing is, perhaps, more striking in her after-life than her unswerving loyalty to the ideals of the Poverello, and the jealous care with which she clung to his rule and teaching.
In 1228, Cardinal Ugolino, having meanwhile ascended the pontifical throne as Gregory IX,  came to Assisi for the canonization of  Francis.   He pressed Clare to so far deviate from the practice of poverty, which had up to this time obtained at San Damiano, as to accept some provision for the unforeseen wants of the community.   But she firmly refused.
On 17th September, 1228, the pope granted her  the celebrated "Privilegium Paupertatis", the Privilege of Poverty.   The original autograph copy of this unique "privilege", the first one of its kind ever sought for, or ever issued by the Holy See, is preserved in the archive at Santa Chiara in Assisi.  After the death of Pope Gregory IX, she had once more to contend for the principle of absolute poverty, for Pope Innocent IV would fain have given the Clares a new and mitigated rule, and the firmness with which she held to her way won over the pope.

In 1234, the army of Frederick II devastated the valley of Spoleto, and the soldiers, preparatory to an assault upon Assisi, attacked the convent of San Damiano.  Clare, calmly rose from her sick bed, and faced the invaders, displaying the Sacrament in a monstrance and praying.  The soldiers took flight. It is with reference to this incident that she is generally represented in art bearing a monstrance.
Some time later, a larger force returned to storm Assisi, headed by the General Vitale di Aversa who had not been present at the first attack,  Clare, gathering her daughters about her, knelt with them in earnest prayer that the town might be spared. Presently a furious storm arose, causing such a panic that attackers left. The gratitude of the Assisians, who with one accord attributed their deliverance to Clare's intercession, increased their love for the "Seraphic Mother".

When Clare felt the day of her death approaching, she called her sorrowing religious around her, reminded them of the many benefits they had received from God and exhorted them to persevere faithfully in the observance of evangelical poverty.   Pope Innocent IV came from Perugia to visit the dying saint, who had already received the last sacraments from the hands of Cardinal Rainaldo. Finally, two days before her death, Innocent, no doubt at the reiterated request of the dying abbess, solemnly confirmed the definitive Rule of the Clares (Bull, "Solet Annuere", 9th August, 1253), and thus secured to them the precious treasure of poverty which Clare, in imitation of St. Francis, had taken for her portion from the beginning of her conversion.
Agnes, had returned from Florence to console Clare in her last illness; Leo, Angelo, and Juniper, three of the early companions of St. Francis, were also present at  Clare's death-bed  and, at her request, read aloud the Passion of Our Lord according to St. John, even as they had done twenty-seven years before, when Francis lay dying at the Porziuncola.  On 11th August, 1253, the holy foundress of the Poor Ladies passed peacefully away.  The pope, with his court, came to San Damiano for the saint's funeral, which partook rather of the nature of a triumphal procession.

The Poor Clares desired to retain the body of their foundress among them at San Damiano, but the magistrates of Assisi interfered and took measures to secure for the town the venerated remains of her whose prayers, as they all believed, had on two occasions saved it from destruction.   Clare's miracles too were talked of far and wide. It was not safe, the Assisians urged, to leave her body in a lonely spot without the walls. She should also have a church in Assisi built in her honour.

Meanwhile, Clare's remains were placed in the chapel of San  Giorgio (now within the enclosure of the church of Santa Chiara), where St. Francis's body had likewise been interred pending the erection of the Basilica of San Francesco.  On 26th September, 1255, Clare was canonized by Alexander IV, and not long afterwards the building of her church was begun.

On 3rd October, 1260, Clare's remains were buried deep down in the earth, under the high altar in the new church, far out of sight and reach. After having remained hidden for six centuries, like the remains of St. Francis, and after much search had been made,  Clare's tomb was found in 1850.  

Finally, on the 29th of September, 1872, the saint's remains were transferred, with much pomp, by Archbishop Pecci, afterwards Leo XIII, to the shrine, in the crypt at Santa Chiara. 

In 1253, Agnes was summoned to San Damiano during Clare's last illness and assisted at her death and funeral. Three months later, on 16th November of the same year, Agnes followed her eldest sister to her eternal reward, as predicted by Clare.   Her mother Hortulana and her sister Beatrice had already passed away. The precious remains of St. Agnes repose near the body of her mother and sisters, in the church of St. Clare at Assisi.
God, who had favoured Agnes with many heavenly manifestations during life, glorified her tomb after death by numerous miracles. She was canonized in 1753 by Benedict XIV.