Curtiss was born possibly in the village of Constantia in Oswego County, New York. His early life and education are undocumented. His mother’s name is not known, but his father was Hastings Curtiss, who about 1820 moved his family to the nearby village of Central Square, where he built a hotel. In 1824 he served a term in the state legislature, and the next year a newly incorporated Oswego County town was named Hastings in his honor. By 1845 Gaston Curtiss had married Floretta Anna Allen and had at least one son, but four years later he was in debt and forced to sell his real and personal property in order to pay his creditors. In 1850 he was living in Hastings, where he was a merchant and a town supervisor. By 1860 he and his family had moved to the port city of Oswego.
Curtiss arrived in Virginia about 1861 but does not appear in the Bedford County records until December 29, 1865, when he purchased 344 acres of land near the town of Liberty (later Bedford) and took up farming. He also became active in the Republican Party. On October 22, 1867, Bedford County voters approved the calling of a convention to write a new state constitution and elected Curtiss and David Staley, both Radical Republicans, as delegates to the convention. An election return published in a local newspaper indicates that all but a handful of white Virginians shunned Curtiss, while he received overwhelming support from the freedmen voting for the first time.
The radical faction of the Republican Party dominated the convention, which met in Richmond from December 3, 1867, to April 17, 1868. Curtiss chaired a thirteen-member committee that organized the business of the convention by identifying the numbers and duties of the standing committees. He also chaired the Committee on the Executive Department of Government, was ranking member of the Committee on Limitations and Guaranties, and at the end of the convention was added to the Committee of Revision and Adjustment. He participated in the convention’s day-to-day business, sat on various ad hoc committees, and spoke often but not at great length on the convention floor. Curtiss aligned with the Radicals on key roll calls and voted with the convention majority on March 6 and 24, 1868, in support, respectively, of a disabling clause and of a test-oath provision that extended, beyond the requirements of the Congressional Reconstruction Acts, the disfranchisement of many white Virginians who had championed the Confederacy. On April 17 Curtiss voted for the new constitution, which included among its reforms universal manhood suffrage, the establishment of a public school system, and more elective local offices. On July 6, 1869, voters ratified the constitution but rejected the two disfranchising clauses.
On January 20, 1869, Curtiss chaired a Republican mass meeting at Liberty, and his son, Allen H. Curtiss, was installed as secretary. The two served on a committee charged with recommending to the state’s military commander candidates for county offices. Allen Curtiss was nominated for county clerk and on January 25 appeared before the Bedford County Court with a letter signed by the military commander, but the next day the court declared him “whol[l]y incompetent” and petitioned for his removal. Later he was appointed clerk of the Third District Court of Appeals, but evidently he did not serve. The military commander also appointed Gaston Curtiss to the Bedford County Court. Curtiss took his seat on March 22 but two days later relinquished it to become assistant revenue assessor.
In March 1869 a Republican convention in Richmond appointed Curtiss to the party’s State Central Committee, and on June 8 of that year Radical Republicans meeting in Lynchburg nominated him as their candidate for the ten-county Fifth District seat in the House of Representatives. The Petersburg Index excoriated the choice and opined that “Curtiss is a very bad man—one of the worst of the whole carpet-bag tribe.” The Lynchburg Daily Virginian expressed similar contempt and in the weeks leading up to the election published a rumor that Curtiss had fled forgery charges in New York. Described as the “loathsome leader of the flock of carpetbag buzzards,” he was also accused of furnishing his home with stolen goods. During the statewide campaign, centrist Conservatives forged an alliance with moderate Republicans that weakened the radical faction of the Republican Party. Curtiss lost the election to Robert Ridgway, whose victory was but one of many for the triumphant Republican and Conservative coalition.
Curtiss returned to farming and died of consumption at his Liberty home on November 15, 1872. In a terse death notice the local press observed, “Probably no man has ever died in any community less regretted than the deceased.” His remains were returned to Central Square, New York, and interred in Hillside Cemetery there. His wife and son were later buried beside him.