It seems likely that there was a Roman presence at the site, as early as the 2nd century, in the form of a caravanserai that may have been associated with the Via Militaris. This early building was almost certainly connected to the nearby fort at Da‘ajaniyya. There is, however, no evidence of any later occupation at the site until the 16th century.

In 1563 Mustapha Pasha lists the site of Khan ‘Unaiza between Hasa and Ma‘an. It is not clear whether this is the Ottoman fort which still stands or the remains of the Roman caravanserai which may have been re-used in the first years of Ottoman rule. However, Barbir, following Mehmed Edib, suggests that the fort was built in, or soon after, 1576, by Sulayman Pasha who was also responsible for the construction of a fort at Hadiya.

In 1709, Murtarda ibn ‘Alawan arrived at ‘Unaiza, carrying water from Hasa because of the heat of the sun. He describes ‘Unaiza as a spacious building, larger than expected, well maintained and not in a ruinous condition. He states that it was owned by the Bani ‘Idha to impress people with their power.

In the early 19th century ‘Unaiza was inspected by engineers working for Muhammad ‘Ali Pasha. They describe the fort as a large square building standing next to a cistern of the same size. The interior of the fort, including the gateway and rooms, was described as being in a ruinous condition and this, combined with the fact that it was only half a day’s journey to Ma‘an, led the inspectors to assert that this stop was not used by pilgrims.

In 1896, Gray Hill visited the fort on his way to Petra after hearing a report that there was water in the cistern. Whilst there he enjoyed, ‘the warmth of a great bonfire of scrub gathered by our men’ and the view of a fine black mountain (Jabal ‘Unaiza). The following year, on 19th March 1897, the German scholars Brünnow and von Domaszewski followed the Hajj route north from Ma‘an and reached ‘Unaiza after a journey of 5 hours and 53 minutes. To the east of the Hajj route, they noted a walled cistern filled with water, which may be identical to the cistern within the compound of the railway station.

In the early 1900s, a railway station was established to the east of the Ottoman fort. In 1916 it became the terminus of a 36 km branch line leading to Shobek, from where wood was collected to fuel the engines of the Hijaz railway.

In 1972 the Jordanian Antiquities Department registered ‘Unaiza as an Antiquities Site and made a basic survey of the fort. In the late 1990s, the fort was included in the Dana Archaeological Survey, which identified the pre-Ottoman building at the site as ‘another large classical site on an ancient road that leads to the Ma‘an oasis’.