This forum was constructed on the order of Emperor Trajan with the spoils of war from the conquest of Dacia, which ended in 106. The Fasti Ostienses states that the Forum was inaugurated in 112, while Trajan's Column was erected and then inaugurated in 113.
To build this monumental complex, extensive excavations were required: workers eliminated the sides of the Quirinal and Capitoline (Campidoglio) Hills, which closed the valley occupied by the Imperial forums toward the Campus Martius.
It is possible that the excavations were initiated under Emperor Domitian, while the project of the Forum was completely attributed to the architect Apollodorus of Damascus, who also accompanied Emperor Trajan in the Dacian campaign.
During the time of the construction, several other projects took place: the construction of the Markets of Trajan, and the renovation of the Caesar's Forum (where the Basilica Argentaria was built) and the Temple of Venus Genetrix.