The district is heavily Latino/Hispanic (predominantly of Mexican descent), as is the surrounding area.

For the 118th and successive Congresses (based on redistricting following the 2020 census), the district contains all or portions of the following counties and communities:[5] Bexar County (3) Democratic challenger Joaquin Castro defeated Republican challenger David Rosa in the race for Texas's 20th district on November 6, 2012.

Democratic incumbent Joaquin Castro defeated Libertarian challenger Jeffrey Blunt in the race for Texas's 20th district on November 4, 2014.

[7] Democratic incumbent Joaquin Castro defeated Libertarian challenger Jeffrey Blunt and Green Party challenger Paul Pipkin in the race for Texas's 20th district on November 8, 2016.

Democratic incumbent Joaquin Castro defeated Libertarian challenger Jeffrey Blunt in the race for Texas's 20th district on November 6, 2018