When Aw Seid built his mosque in the southern part of the current site of Galamso town, the Oromo started to call it galma Usso.

Based on figures from the Central Statistical Agency, the result of the third Ethiopian census shows that Galamso has total population of 210,000 of which 113,003 are male and 107,481 are female.

Today, as Professor Urlich Braukamper had described precisely in his book, the remnants of the stone built necropolis, store pits, houses and mosques of the ancient Harala people are observable in all of the Hararghe highlands.

[4] However, some of the most notable scholars who studied the case deeply, such as Ulrich Bräukamper, suggest that the Islamization effort of Aw Seid could be a phenomenon of latter ages (i.e. after the 16th century),[4] an argument that has a good ground, as far we consider the starting period of the mutual interdependence between the Muslims of the southeast and their Oromo neighbors.

[17] Here, as many books have recorded, it was also Aw Seid who played a key role in the derivation of the Oromo Constitutional Law (called Hera) at Oda Bultum.

And many rituals exercised when the Ya'ii[3][17] (conferences) of the Chaffe Gada were undertaken at Oda Bultum in recent years were called in the name of Aw -Seid.

[17] Some people say Gelemso was an administrative capital and the seat of the Mana Bokkuu (the President's Office) of the Eastern Oromo, with Oda Bultum serving as the place where Caffee Gadaa assembled only once in eight years.

Latter on, oral history says, Gelemso evolved to an important village of commerce when one of its counties called Qabri Lukku (now found in the south eastern tip of the town) was organized as a market center to accommodate traders who were coming from different regions.

(Qabrii Lukku mean grave of Lukku) To conclude, when we consider oral histories which assert the town had Karra Torba (The Seven Gates) in ancient times, non existent in the case of other towns of West Harerghe save Gelemso, when we consider its presence closer to places of significant traditions like Halayya Buchuro[17] and Laga Bera (retold as a place where once ruthless and contestant dictatorial queen called Akkoo Manoyye had built her palace), when we analyze its tie to Oda Bultum and the presence of the shrines of Aw-Seid both at Gelemso and Oda Bultum, we can deduce that Gelemso must had been a place of higher social and spiritual importance in the tradition of the Oromo people since ancient times.

In 1887, while campaigning to occupy the city state of Harar and the whole of Eastern Ethiopia, which he accomplished after his victory at the Battle of Chelenqo,[3][9][23]: 72  Emperor Menelik II had arrived at the bottom of the current Gelemso town.

It is said that Menelik II had an aim of erasing the centrality and symbolism of early places like Gelemso from the mind and the heart of his Oromo subjects.

Truly speaking, it was Emperor Menelik II who officially closed down all of the traditional Oromo institutions like Chaffe assembly and prohibited many other cultural feasts,[3][9] a fact that Ethiopian writers of the early 20th century like Aleqa Tayye had recorded.

Bahru Zewde narrates that in 1933, immediately after his ascension to the throne, Emperor Haile Selesie made Chercher awraja the model of his future administration system.

During their five years administration, the Italians returned the seat of the Chercher province to Gelemso (which was moved first to Kunni, then to Asebe Teferi or Chiro by the Haile Selassie officials) and made valuable change on its urban customs.

They established new settlements in the northern and eastern parts of the town, starting from a hill called now Kambo (from Italian campo which mean a military camp).

(The remnant of the western old road still exists with its decorated Italian style bridge built on the northern section of Aw Seid river).

Although the group closed its missionary activities in the 1960s, the school they built has continued to function to this day, and the elderly people still call it Amerikaanii (The American).

For example, the town was equipped with electric light service for 6 hours a night, and its tap water supply system (built by Italians) was expanded.

However, it was the efforts of Arabian, European and Asian traders that greatly helped Gelemso continue its long standing role as market center and social panorama.

The list of those foreign traders includes Nasir Sana'ani, Abdallah Ubadi, Ali Ahmed, Ali Sa'ad, Salah Muhsin who were all Yemenis, the Greeks Kostar Gragor and his brother Stafrol, the Italians Antonio Viccini and Francesco Berto, the Sudanese Haji Abdullah and Sheikh Bashir Babikir, and the Indian Usma'il Hindii.

Latter on, natives of the town like Mohammad Abdo (Lungo), Ahmed Yusuf, Mohammed Beker, Muteki Sheikh Mohammed and his brother Ahmad Taqi, Haji Ahmed Nure, Haji Sani Abdulqadir, Ahmed Alhadi, Usmail Ahmayyu, Nejash Usmail, Belew Haile, Mekonnen Metaferia, Jemaneh Yimamu, Tiruneh Gebremichael, Omar Ghazali and his brother Mumme Ghazali etc....and well known Ethiopian entrepreneurs like Mohammed Abdullahi Ogsade also entered to the business and they altogether marked the town's classic commercial era.

[28] In the late 1960s and early 1970s, General Taddese Birru, a well known Oromo nationalist and co-founder of Mecha-Tulama Self Help Association,[23]: 273 [29] had been in the town for his supposed ግዞት (Amharic for house arrest) .

The 1984 Harerghe Province All Games Championship it hosted was the major sport festival in history of the town where all of the 13 awrajas in Hararghe participated in the contest.

One of the main urban zones of the town, called in its Amharic name Addis Ketema (the New City), totally emerged during the Dergue time as well.

For instance, the residents of Gelemso still have fresh memories of the Kara Qurqura Massacre where 70 people (half of them in the pretext of Amhara land lords who resist the land reform, and half of them labeled Oromo secessionists who conspire against the state with Somali Expansionists)[31] were taken away from town, executed, and then bulldozed to one grave in April 1970 at a place called Karra Qurqura.

In similar way Dergue military groups massacred 32 innocent civilians (children, baby of 1 year, women and elderly) bulldozed and buried in one grave yard in the place called 'Biyo' few km from town of Michata.

On May 30, 1991, the town came under the control of the Oromo Liberation Front (OLF) and was made the administrative center of the OLF-held areas in the former provinces of West Hararghe, Arsi and Bale.