It was built above the former Inguarán Avenue (now Congreso de la Unión) in viaduct solution, this makes it the only line without an underground section.

[1] The line is also characterized by its above-ground architecture, having all of its station facilities elevated or in massive buildings present in both sides of the street.

[6] The second stage of the line was opened for service on 26 May 1982, with four new stations, going from Candelaria to Santa Anita.

In 1985, according to a plan presented by the Comisión de Vialidad y Transporte Urbano (COVITUR), Line 4 was projected to be expanded southbound from Santa Anita towards Culhuacán, the stretch would have a length of 9.22 km (5.73 mi) and seven new stations.

In 1996, the Sistema de Transporte Colectivo (STC) on its master plan for Mexico City Metro considered building an expansion for Line 4; this time, it would be expanded northbound from Martín Carrera to Ecatepec in the State of Mexico.

Thirty-one more stations would be built according to the plan: ten southbound and 21 northbound, adding a total of 34.87 km (21.67 mi) to Line 4.