Club Leon

The club was created from an application by Unión de Curtidores which merged with Selección de Guanajuato. With the money raised, the directive hired Marcial Ortiz, Raúl Varela, Alfonso Montemayor, Salvador Ramírez, Conrado Muñiz, Vicente Serrano, Pepe Cortes, "Sticks" Ramírez, Elpidio Sánchez, and Joaquín Source Duillo Dobles. It participated in the Liga Mayor's second season (1944–45). The team comprised Argentine players and Miguel Rugilo that served as coach and goalkeeper holder. Battaglia played defense plus two fronts; Marcos Aurelio scored 14 goals with Ángel Fernández. The team debuted at the Patria stadium on August 20, 1944, against Atlante and lost by a score of 5–3.

In the 1945–46 season, another team appeared in the city: the San Sebastián de León. They placed fourth out of 16 teams with 30 games, 17 wins, 4 draws, 9 losses for 38 points. Their top scorer, with 24 goals, Alberto Mendoza.

In the 1946–47 season notable players joined, one of whom was Adalberto López, who scored 33 goals. In general, the team had a great campaign being runner-up with 41 points and maintained a fourteen-game winning streak. Another important element was Marcos Aurelio, who highlighted with 16 goals. A match against Atlante was scheduled place in Mexico City on June 1, 1947, in the Estadio Insurgentes (now Estadio Ciudad de los Deportes) which took place in León, but had to switch venues due to an epidemic of foot-and-mouth disease afflicting the Bajío region

In a match against América on May 9, 1946, Florencio Caffaratti accidentally touched an electrical wire after scoring a goal. Alfonso Montemayor rescued him. Subsequently, Caffaratti gave a gold coin to Montemayor with the inscription: "In appreciation of Montemayor by F. Caffaratti."

1947–48

When José María Casullo coached Club León, the greens lost seven times, three of them against Atlas. The team tied at 36 points with the Jalisco Gold at first place. Jalisco Gold broke the tie with a score of 2–0.

1948–49

Club León defeated Asturias 2–0 with goals by Adalberto López to prevent a tie with Atlas and Guadalajara who remained a point, and Leon became the first to win the tournament campeonísimo cup after defeating Atlante 3–0 on August 14, 1949.

1951–52

Club León switched coaches to Antonio López Herranz. Antonio Carbajal joined the team with the return of Marcos Aurelio, Sergio Bravo, and Saturnino Martínez. The team played against a Guadalajara team coached by José María Casullo. León won both games of the year with scores of 1–0. In the penultimate round, León lost to Guadalajara by 1 point.

In the following season, the team remained in third place at 27 points. For the 1953–54, season it finished in eighth place with 21 points.

1955–56

The season's roster increased to 14 teams. León won the best streak in club history with 12 wins and 7 draws before losing against Tampico (1–0). The final game was played at the Estadio Olímpico in Mexico City, where León defeated Oro (4–2) and Toluca.

In 1956–57, León lost to Guadalajara. In 1957–58, they reached fifth place but won the Copa MX title.

1960s

León remained in fifth place in the 1960–61 season with 26 points, fifth place in the 1961–62 season with 25 points, ninth place in the 1962–63 season with 25 points, ninth place in the 1963–64 season with 25 points, seventh place in the 1964–65 season with 30 points, ninth place in the 1965–66 season with 28 points, fifth place in the 1966–67 season with 34 points, fifth place in the 1967–68 season with 35 points, seventh place in the 1968–69 season with 31 points, and seventh place in the 1969–70 season with 31 points.

1970s

For the Mexico 1970 World Cup, there were two technical changes: the starter Argentine Luis Grill was replaced, but was reinstated after Antonio Carbajal left, as a result, left with 33 points to fourth overall Sergio Anaya new stand becomes scorer the contest with 16 touchdowns, while Luis Estrada scored 13 goals. 1970–71 players arrive, Jorge Davino, Roberto Salomone and Juan José Valiente who scored ten goals, the club was led by Carbajal and ranked fourth with 38 points.

In 1972–73, Antonio Carbajal was replaced by Rafael Albrecht who served as player and coach. The final game was against Cruz Azul.

In 1973–74, the team failed to qualify at fifth place with 40 points.

First relegation

In 1986–87, Jorge Davino scored 10 points in 19 days and León was subsequently relegated to the Segunda División de México. However, they would reappear in the Primera División de México on May 10, 2012 and won the Apertura 2012 when they arrived back to the Primera División.

1990s

The Esmeraldas returned to the Primera División for the 1990–91 season and were coached by Víctor Manuel Vucetich, who debuted in the top flight and led the entire tournament. He led the club in sixth place with 41 points, but did not qualify to be third in group 3, and Martin Uribe and Francisco Peña highlighted with 13 and 12 goals.

Second relegation

Robert Zermeño cost the team and landed them in last place with 19 points.

After the second relegation, the club was sold to Argentine businessman Carlos Ahumada.

On November 19, 2010, Grupo Pachuca purchased the club.