1140: St. Bernard of Clairvaux sent Cistercians, under the leadership of Bernard Pganelli, who was the first abbot before being elected pope under the name of Eugene III in 1145.
The abbey was held by Cistercians until 1826, but was pillaged by revolutionary armies and counted only a small number of monks.
1826: Given to the Observant Friars Minor. They remain until 1867, but the monastery decays even further.
1867: Trappists took over at the invitation of Pius IX.
1868: A Brief of 21 April grants the community use of the monastery, three churches and a small property. One of the first occupants is Fr. Franz Pfanner, future founder of Marianhill.
1870-71: The community is dissolved by a rapacious government. The monks were allowed to remain as guardians and received a salary.
1874, 11 November: The monks form an agricultural corporation.
1886, 8 April: The acts of “affrancazione”. The community, being an agricultural corporation, becomes owner of the property by the payment of an annual royalty. The monastery lands had long been infested with malaria. Many monks came down with the disease and paid for their devotion with their lives. The community need help to live and to pay the annual indemnity.
1892: At the union of the 3 Trappist congregations it was decided that the abbot general would be abbot of Tre Fontane and reside there. In fact, that never came about, but in view of this arrangement the community is governed for some time by priors.
1894: A monk of Sept-Fons, Fr. Leon Ehrard, is sent to Tre Fontane. He becomes cellarer, then prior, and finally abbot in 1919. His hard work and intelligence transform the situation and the abbey flourishes both spiritually and materially.
1936: The community is juridically recognized, according to the laws of the Concordat with Italy and the property of the agricultural corporation was transferred to it. The annuities had been paid.
1942: Part of the property was expropriated for the construction of a future exposition (E.U.R. – Esposizione universale di Roma), which never took place. This became today’s EUR district.
As the city of Rome expanded, the greater part of the property had to be sold. Today only 30 hectares remain.