As he lay dying in the stables to which he had been condemned to labor, the aged Pope Marcellus I would hardly have imagined that this church in his name would one day stand on this site.  Elected in 308, he was faced almost immediately with the issue of the re-admittance to communion of those who had denied the faith in the persecutions, to which issue he responded by upholding the traditional period of penance.  Arrested some months later, he was made to work in the imperial stables just off of the main road which is now the Via del Corso.  Some traditions say that this had been the location of an oratory consecrated by him, turned into stables by the Romans to humiliate him and the Church.  After suffering in the difficult labor, he would die shortly thereafter.  Another tradition relates that he was sent into exile after his arrest, dying there sometime later although his relics were returned to Rome.  In the late fourth and early fifth century, the first church was built here in his honor as part of a program to replace house churches with larger structures.  This would soon enter into history for the dubious honor of being the seat of the antipope Boniface in 418, a role it would again serve in the early twelfth century when another antipope occupied the church.  A baptismal font, built sometime soon after the fifth century, was present here, of which the remains were discovered in 1912.  This marks the church as being of some significance, since the ordinary place of baptism was still the Lateran.  Adrian I undertook repairs here in the late eighth century, and sometime in the early twelfth century the church was completely demolished and replaced with a new one.  However, a fire on 23 May 23, 1519 would cut the life of this church short, with the most significant survivor of the disaster being a crucifix, now venerated in a side chapel.  Beginning in 1525 and continuing for the next 70 years, the work of reconstruction took place, with the orientation of the church being reversed to that the façade faced the Via del Corso.  The later years of the seventeenth century would see some final modifications to the site, as the Romanesque campanile was demolished and the current façade, designed by Carlo Fontana, was constructed.  The interior was restored in the 1860s, and it is in this form that the building comes down to us today.