From 1979 onwards, votes cast in the district also counted towards the calculation of proportional representation ("plurinominal") deputies elected from the country's electoral regions.

[1][2] The 25th, 26th and 27th districts were abolished in the National Electoral Institute's 2017 redistricting process because the capital's population no longer warranted that number of seats in Congress.

[3] In its final form, when the capital accounted for 27 districts, the 26th was located in the south-west of the city.

The 26th comprised the borough of Magdalena Contreras and the adjacent south-west portion of Álvaro Obregón.

[5][7] The districting scheme in force from 1978 to 1996 was the result of the 1977 electoral reforms, which increased the number of single-member seats in the Chamber of Deputies from 196 to 300.