Relegated in 2005 after losing 3–0 to Deportivo Pereira, Unión earned automatic promotion to the 2019 Categoría Primera A season, after playing 13 years in the second division football league.

[4] Red and blue stripes compose the traditional shirt of the team, and its design is inspired by the Argentine club San Lorenzo de Almagro.

However, video footage of Unión Magdalena's winning goal appeared to show the Llaneros players backing off and failing to make an effort to prevent their rivals from scoring.

[6][7][8] In response to the growing backlash, as well as calls from Fortaleza to get the match annulled and Unión Magdalena's promotion reversed,[9] Dimayor chairman Fernando Jaramillo ordered the opening of an inquiry on the match events while also requesting the Office of the Attorney General of Colombia to investigate whether any criminal offenses had been committed,[10][11] but on 7 December 2021, Jaramillo stated that the tournament would not be paused and Unión Magdalena's promotion would not be overturned while due process was completed.

[12] However, amid the ongoing inquiries, the Torneo II's final match between Cortuluá and Unión Magdalena, which was originally scheduled to be played on 11 December 2021 in Tuluá was postponed until further notice.

[13] On 30 December 2021, Dimayor's disciplinary commission closed the investigation on Unión Magdalena as it found no evidence implying that members of the aforementioned club had been responsible for the events that occurred in the match against Llaneros, thus confirming their promotion to Primera A for the 2022 season.

[citation needed] After the inauguration of the Sierra Nevada Stadium for the 2017 Bolivarian Games, the Union Magdalena agreed with the mayor of Santa Marta official to return to the city from the 2018 season.