[3] It is named for James Harper Starr, who served as secretary of the treasury of the Republic of Texas.

Starr County comprises the Rio Grande City micropolitan statistical area, which also includes other small cities, which itself is part of the larger Rio Grande Valley region.

[6] As of the 2020 United States census, 65,920 people, 16,281 households, and 12,836 families were residing in the county.

Jack Herrera of Texas Monthly stated that "That means the county isn’t just one of the most Hispanic in the country.

[19] In the 1970s and into the 1980s, federal law-enforcement officials concentrated their efforts against drug smuggling on Starr County.

[20] On May 1, 2009, the former sheriff of Starr County, Reymundo Guerra, a Democrat, pleaded guilty in federal court to a narcotics conspiracy charge.

[21] In April 2016, Starr County Justice of the Peace Salvador Zarate Jr., faced up to 20 years imprisonment and a $10,000 fine on two counts of bribery for accepting a $500 bribe in exchange for reducing bond on two persons arrested on narcotics charges in an incident on Christmas Eve 2014.

In 2024, Donald Trump became the first Republican since 1892 to carry the county, ending over 130 years of Democratic dominance.

[26] In 1988, the county gave Michael Dukakis his highest vote share in the nation, as well as Bill Clinton in his 1996 re-election bid.

[28][29] This was a major shift from Hillary Clinton's 60-point margin of victory four years earlier, and represented the strongest pro-Trump swing of any county in the nation.

[16] In the 2024 United States presidential election, Trump received a majority of the votes in Starr County.

[30] With Trump's victory, this marked the first time a Republican candidate won the county in a federal election.