Union has since its foundation on 2 July 1900 – where it was named NKUB (Nordvestkvarterets Kristelige Ungdomsforenings Boldklub) – had a strong affiliation to the Nordvest neighbourhood.

Four years later, it assumed the status of joint club for the entirety of Nørrebro's YMCA (KFUM) and thus adopted the name "Union".

Because Union had to share the wealth with other clubs affiliated to Københavns Idrætspark, which affected its youth department, the board sought a new home ground.

With the move, Union achieved its own home ground and remained the only club in the area, which generated a new influx of young players.

[3] The club had earlier delivered youth prospects such as Viktor Tranberg and Frederik Holst to the Danish Superliga side.