George B. McKinstry, soldier and civil servant, was born on July 12, 1801, in Ireland. He arrived in Texas, probably from Georgia, on April 20, 1829, and took the oath of citizenship on May 19. In Stephen F. Austin's Register of Families he is listed as a trader. On December 15, 1829, he purchased two building lots and one garden lot in San Felipe de Austin. In 1830 he was appointed the first postmaster of Brazoria. During his residency in Brazoria he engaged in coastal trade. On December 16, 1831, a meeting of Brazoria citizens appointed McKinstry and Branch T. Archer to seek a repeal of a recent decree that had closed all Texas ports but Anahuac, on Galveston Bay. Refused satisfaction by George Fisher, customs agent at Anahuac and author of the decree, the men approached Juan Davis Bradburn, commander at Anahuac, threatening an attack on his fort if their demand was not granted. Bradburn acquiesced and sent an agent to the Brazos to collect duties. McKinstry later wrote that while he and Archer were in Anahuac, they "entered into a secret understanding with [William Barret] Travis and some others to resist...unlawful proceedings" by the Mexican military and customs officials. They also arranged for the purchase of "powder lead and flints" in New Orleans. In a letter of February 6, 1832, condemning the action taken by the Brazoria colonists, Stephen F. Austin also expressed extreme concern about the imprudence of certain individuals, including McKinstry, who publicly boasted that Brazoria had subscribed $800 for the purchase of powder and arms.
In the summer of 1832 McKinstry participated in the effort to release Patrick Jack and others from jail during the Anahuac Disturbances. On June 10 he was one of a group of American colonists who met unsuccessfully with Bradburn to seek release of the prisoners. On June 20, together with 103 others, including John Austin, W. H. Wharton, and Edwin Waller, McKinstry signed an agreement at Brazoria organizing a military unit composed of Austin colony recruits. The next day he and others received orders from John Austin to seize the arms and ammunition at Brazoria from the Mexican collector of customs. Taking two cannons from Brazoria and loading them on a schooner, McKinstry and his group sailed down the Brazos River. At Velasco, however, near the mouth of the river, the Mexican commander refused them permission to pass. In the ensuing battle of Velasco, the colonists used powder and lead that McKinstry had helped secure in New Orleans. After the battle McKinstry, elevated from sergeant orderly to lieutenant, commanded the captured fort for an undetermined period. Meanwhile, before McKinstry's companions could transport their armaments to Anahuac, Bradburn relinquished his command there, and the prisoners were released. In September the customs agent at Brazoria, Francisco Mansue y Duclor, whose store of weapons had been seized by McKinstry and his unit, received permission from the customs agent at Galveston to return to Tampico.
At the Convention of 1832 McKinstry was one of four delegates representing the Victoria District. During that meeting he served on a committee chosen to draft a petition to the federal government requesting the reduction of import duties on "articles of the first necessity." Stephen F. Austin, who presided over the convention, remained critical of him. In a letter of May 30, 1833, Austin deplored the departure of Duclor, "a Santa Anna officer," from Brazoria, an event he attributed chiefly to McKinstry. Austin wrote that the colonists' intemperate actions at Brazoria and Anahuac had damaged their position with Antonio López de Santa Anna, and that McKinstry had "done as much harm to Texas as any man in it."
At a public meeting in Columbia (now West Columbia) on June 28, 1835, McKinstry, with John A. Wharton and a number of other local notables, was chosen to report on conditions in Texas. They prepared a resolution condemning the declaration of colonists in Anahuac on May 4, 1835, that they would pay no customs until the collection of duties was enforced at other Texas ports. The Columbia resolutions also recommended "[continued] union [with Mexico], moderation, organization and a strict adherence to the laws and constitution of the land." At another meeting in Columbia on December 25, 1835, however, McKinstry was among those voting in favor of a declaration of independence. After the battle of San Jacinto, McKinstry formed part of the volunteer guard that escorted Santa Anna and other Mexican prisoners to Galveston and then on to Velasco.
In January 1834 he bought two male slaves through William B. Travis, and the following April he contracted with Travis for three more. On November 25, 1836, McKinstry sold Simon, a slave about twenty-seven years old, to Stephen F. Austin for $1,200. On December 20, 1836, President Sam Houston appointed McKinstry the first chief justice of Brazoria County. Stephen F. Austin died at McKinstry's home in Columbia on December 27, 1836. In May 1837 McKinstry was among a group of men who secured a charter for a railroad to be built between Galveston Bay and the Brazos River. He died in Brazoria on December 10, 1837, and was buried in Columbia. He left a wife, Ann C., and an infant son, who was named after him. Ann McKinstry subsequently petitioned for a court order providing for the sale of land from her husband's estate to settle claims of $1,350. In 1840 her taxable property included five slaves, 163 acres, two town lots in Brazoria, and one workhorse. On January 14, 1841, in Travis County, she married Greenberry Horras Harrison.