Founded on 1956, the Ademar León is the handball team more representative of the city of León. Until 1975 it played in the provincial categories when not existing economic availability to be able to promotion. In that year the team promoted to 1ª División Nacional (being player of the team the currently chairman, Juan Arias).
His 6th place in season 95/96 allowed him to play for the first time in its history a European competition (City Cup).
In season 96/97 Runner-up of ASOBAL League, and runner-up of ASOBAL Cup was able to proclaim itself, being third in the King's Cup and obtaining seat to play the Champions League in the following season.
The beginning of the 2001–02 season caused the first misfortune when losing the first title of the year, Supercopa of Spain, in Tudela losing the final against Portland San Antonio, champion of Cup in the previous season.