[5] The abandonment of Fort Duncan on March 20, 1861, during the Civil War, enabled the Indian population to gain control of the region; both American and Mexican inhabitants suffered tremendous loss of life and property.

[6] In early 1871, a number of Black Seminole Indians living along the border were organized into a company of scouts and brought to Fort Duncan.

[8] The trail was originally blazed by Alonso De León in 1690, and is said to have been traversed by more early Spanish explorers and settlers than any other section of the state.

[12] In 1675, Fernando del Bosque traversed the area near Quemado, and Franciscans with the expedition are said to have celebrated the first Mass on Texas soil.

[13][14] In 1688, Alonso De León followed the Camino Real across the county en route to Fort St.

[15] Domingo Terán de los Ríos, the first Governor of Spanish Texas, led an expedition through the county in 1691.

[16] Spanish Texas Governor Martín de Alarcón crossed the county in 1718 on the expedition that resulted in the founding of San Antonio.

[18] Pedro de Rivera y Villalón crossed the county in 1727 as part of an expedition to inspect the frontier defenses of New Spain.

[6] General William Leslie Cazneau, credited several years earlier with burying the Alamo casualties with full military honors, began ranching in the area around 1850.

He partnered with Irish-born San Antonio banker and county settler John Twohig to lay out a plan of Eagle Pass in 1850.

[20] Freight operator Friedrich Wilhelm Carl Groos secured a contract to haul supplies for the army at Fort Duncan.

[21] Emigres Refugio and Rita Alderete de San Miguel used the profits of their freighting business to establish a large-scale cattle, sheep, and horse ranch on Elm Creek in 1853.

They were joined in ranching operations by stranded pilgrims on the California Gold Rush trail and discharged Fort Duncan soldiers.

Among these was Infantry veteran Jesse Sumpter, who also worked at many odd jobs before becoming sheriff in the newly formed Maverick County.

An international incident was brought about by James H. Callahan and William R. Henry, whose pursuit of Lipan Apache raiders and runaway slaves into Mexico ended in the looting and torching of Piedras Negras, after an encounter with Mexican forces at La Marama on the Río Escondido.

Eagle Pass was a major terminus of the Cotton Road, custom house and Confederate port of entry into Mexico 1863–65.

At the close of the Civil War, General Joseph Orville Shelby's brigade never surrendered, but hoped to continue their fight across the border.

Thompson died in 1910, but his efforts came to fruition as the Maverick County Irrigation Canal system, operational by April 1932.

[24] March 3, 1911, when Lt. Benjamin D. Foulois and Philip O. Parmalee made the first official military reconnaissance flight, looking for Army troops between Laredo and Eagle Pass, Texas, with a ground exercise in progress.

In 1942, the Army Air Force built a single-engine advanced flying school 12 mi (19 km) north of Eagle Pass.

Industries which have located in the Eagle Pass–Maverick County area since 1977 include the Eagle Pass Manufacturing Company (a division of Hicks-Ponder, Inc) and the Williamson-Dickie Manufacturing Co, both makers of work clothing; the Reynolds Mining Corp fluorspar plant and the Tejas Barite plant; Alta-Verde Industries and Maverick Beef Producers, and the Big River Catfish Farm.

The 2024 election continued this trend, in which the county flipped Republican by a large margin, casting nearly 59% of its vote for Trump.