[1] It elects one deputy to the lower house of Congress for each three-year legislative session by means of the first-past-the-post system.

Votes cast in the district also count towards the calculation of proportional representation ("plurinominal") deputies elected from the fifth region.

Its head town was at Lázaro Cárdenas and it covered nine of the 2022 municipalities, with Ario assigned to the 11th district.

The 1st district's head town was at Lázaro Cárdenas and it comprised the municipalities of Ario, Arteaga, Churumuco, La Huacana, Lázaro Cárdenas, Múgica, Nuevo Urecho and Tumbiscatío; i.e., the 2022 municipalities, minus Gabriel Zamora and Parácuaro.

[9][8] 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.