In response to requests from French bishops, Pope Pius IX promulgated the feast of the Sacred Heart in 1856.
The basilica itself was consecrated on 16 October 1919.

Since 1885 (before construction had been completed) the Blessed Sacrament (Christ's body, consecrated during the Mass) has been continually on display in a monstrance above the high altar.
Perpetual adoration of the Blessed Sacrament has continued uninterrupted in the basilica since 1885.
Tourists and others are asked to dress appropriately when visiting the basilica and to observe silence as much as possible, so as not to disturb persons who have come from around the world to pray in this place of pilgrimage, especially since there is the exposition of the Blessed Sacrament.
Photos are not allowed to be taken in the Basilica.
In response to requests from French bishops, Pope Pius IX promulgated the feast of the Sacred Heart in 1856. The basilica itself was consecrated on 16 October 1919.
Since 1885 (before construction had been completed) the Blessed Sacrament (Christ's body, consecrated during the Mass) has been continually on display in a monstrance above the high altar. Perpetual adoration of the Blessed Sacrament has continued uninterrupted in the basilica since 1885. Tourists and others are asked to dress appropriately when visiting the basilica and to observe silence as much as possible, so as not to disturb persons who have come from around the world to pray in this place of pilgrimage, especially since there is the exposition of the Blessed Sacrament. Photos are not allowed to be taken in the Basilica.
Sacré-Cœur, Paris