Upon the death of St. Francis, which occurred near the Porziuncola on October 3, 1226, his body was carried from the chapel in the woods of the valley to the Chiesa di San Gior­gio (St. George), near Assisi, to avoid possible attempts of theft by rival Perugia. On March 29, 1228, Simone di Pucciarello, citizen of Assisi, donated to Brother Elia, both in the name of and on behalf of Pope Gregory IX, a tract of land in the hamlet of Colle dell'lnferno (Hell Hill). This area was once used for executions and is located at the bottom of the hill where the slope ends abruptly in the direction of the Tescio River Valley. On April 29 Gregory IX announced that he wished to build an ecclesia specialis (special church) which would function both as a tomb for the saint and a caput et mater (head and mother) for the Minor Order, granting indulgence to all who would help with the con­struction of the Basilica. Brother Elia was assigned to collect donations for the construc­tion of a church and Convento for the religious. On July 17, the day after the canonization of St. Francis, Gregory IX laid the first stone of the new church. According to the original plan, the building should have been very plain, inspired by the ideals of poverty of the ear­ly Franciscan movement. The construction proceeded rapidly and, on May 25, 1230, the body was entombed in a cell which had been prepared for it under the main altar. After the appointment of Brother Elia as head of the Order (1232-39) the idea changed to that of making the monument a visible proof of the extraordinary influence of the Franciscan movement. The part which had already been built was turned into an enormous crypt which, due to the steep slope of the site, became the base for a second church and served as a classroom for the monastery, a church for preaching, and a papal chapel. The original trussed ceiling was replaced with massive cross vaults with large ribs in the Lombard Ro­manesque style. Franciscan sources give the credit for the construction to Brother Elia, who personally supervised the construction of the cross vaults. ,
When Brother Elia fell out of favor, after being excommunicated by Gregory IX in 1240 for the friendship which linked him with Emperor Frederick II, the Englishman Hymen of Faversham became the new head of the Order. It was probably due to his influence that workers from the North were called to Assisi, bringing with them the slender and elegant forms used in the luminous hall of the Upper Church, forms which are comparable to ex­amples from the Anjou Gothic. The names of the architects who designed the project are not known. Giorgio Vasari attributes the project to one Jacopo Todesco, father of Amolfo di Cambio. Nineteenth century German historiography praises the role of Filippo da Campello who, however, seems to have been more an administrator than an architect. An­other hypothesis attributes the project to master Paolo Luprandi, cited as a witness in a document of 1239. Finally, still another source identifies the architect as Brother Giovanni da Penna, who in 1238 built the aqueduct which brought water to the Convento. The con­struction of the Basilica was brought to completion within a period of 20 years. It must have already been finished in 1253, when Innocent IV solemnly consecrated the altars and appointed Filippo da Campello in charge of the decoration, with permission to use as funds the donations left by the pilgrims.
In addition to the church, Gregory IX promected the costruction of  a papal palace and a Convento, used as early as 1230 by community of friars; the papal palace was finished before 1239 ; Brother Elia was living here greatly scandalizing his fellow brothers . The convento was enlarged several times between 14th and 15th century and assumed its final form during the rein of Sixtus IV (1471 – 1484) who order the costruction of the cloister  and the great scarp wall facing Perugia, on which a very large portrait of him was placed. After the expropriation of the ecclesiastical estates following Italian unification, the Convento became the property of the State, which used it as a boarding school for or­phans. In 1929 it again became the possession of the monastic community.
Externally, the Basilica consists of two independent churches, one superimposed upon the other. Each church has a single nave and transept, but they are not identical, for the tran­sept of the Lower Church juts out further than that of the Upper Church. The entire com­plex of Church and Convento was designed so as to be seen in a foreshortened view from the lower piazza, due to the steeply sloping terrain which also prevented the construction of the facade of the Lower Church, accessible only from a side entrance. The Upper Church has a simple gable facade. It is constructed entirely of white limestone, with the exception of the enormous pink stone buttresses, six on each side: These turrets are said to have been made in honor of the twelve apostles. They are in pink stone in memory of their martyrdom and the shedding of their blood for the sake of Christ. (Brother Ludovico da Pie­tralunga, about 1570). The unusually high apse is divided into two parts by a cornice. The lower part is semicircular in form and is supported by sturdy, flying buttresses. The upper part is polygonal and has three large windows. On the left side is the also unusually high Romanesque bell tower, built at the same time as the church and perhaps already finished when a bell was cast for it in 1239. It is divided into three levels by cornices of small hang­ing arches divided by pilasters and ends with a belfry opened by three arches. The belfry was topped by a cusp which was tom down in 1530.

Texts Kindly offered by: Editrice Minerva Assisi