The cities of Sofia and Plovdiv have traditionally been the biggest and most developed in Bulgaria, including sports wise.
Prior to the creation of A PFG in 1948, Lokomotiv Sofia was among the most prominent Bulgarian teams, winning two national titles.
Since then, the two teams have almost always regularly played each other in the top tier of Bulgarian football, with brief relegations for both sides.
Things changed, however, when Lokomotiv Sofia won their fourth national title in the 1977-78 season, surprising many.
After 1989, the communist regime was overthrown, which resulted in the privatization of the economy, including football clubs.
On the other hand, Lokomotiv Plovdiv, began a downward spiral in terms of results, finishing behind their rivals in the following years.
Following this, the owners of Lokomotiv Plovdiv decided to save the club by merging with Belasitsa Petrich, but keeping their name.
The early 2010s were not memorable for either of the two clubs, with Lokomotiv Sofia barely avoiding relegation during the 2011-12 and 2012-13 seasons.
During the 2014-15 season, Lokomotiv Sofia finished third, but was administratively relegated to the third tier for financial problems, which was the result of several years of bad management in the club.