Leganés played the vast majority of its existence in the lower leagues. In 1977 the club regained promotion to the fourth division, where it had played before for seven years when the category was still the third level.
After a steady progression, Leganés reached the new division three in 1987, being promoted to the second division six years later and maintaining its league status for 11 seasons; during this timeframe, it collected two consecutive eighth places (best) from 1995–97.
In the 2015–16 season, for the first time in their history, Leganés earned promotion to La Liga, which was sealed on 4 June 2016 with a 1–0 away win against CD Mirandés.
On 24 January 2018, Leganés qualified for the first time to the semifinals of the Copa del Rey, by eliminating Real Madrid in the quarterfinals thanks to a 2–1 win at Santiago Bernabéu Stadium.
Source: Wikipedia