[1] It elects one deputy to the lower house of Congress for each three-year legislative period 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 third region.

[a] The district's head town (cabecera distrital), where results from individual polling stations are gathered together and tallied, is the city of San Juan Bautista Tuxtepec.

[11][10] 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.

[12] The 1st district had its head town at Juchitán de Zaragoza on the Pacific coast of the Isthmus of Tehuantepec.