Thomas Allen Jenckes was born in Cumberland, Rhode Island on November 2, 1818. He attended public schools, followed by Brown University in Providence, from which he graduated in 1838. He subsequently served as Tutor in Mathematics at Brown (1839-1840) while reading for the law in the office of Samuel Young Atwell (Brown Class of 1814). He was admitted to the bar in 1840.
Jenckes practiced law in Providence, developing an expertise in patent cases. He was particularly noted in his own time for his work on the Sickles and Corliss steam engine patents, and on the Day and Goodyear rubber cases. He was also retained to represent the United States in its case against Credit Mobilier. During the Dorr Rebellion, Jenckes served the Charter authorities under Governor Samuel Ward King, and became Secretary of the newly formed Governor's Council. He also participated in both the Landholders Convention of 1841 and the state Constitutional Convention in 1842. He held the posts of Adjutant General from 1845-1855 and Commissioner assigned to revise the Rhode Island code in 1855; and was an elected member of the State house of representatives from 1854-1857.
In 1862, Jenckes was elected to Congress as a Republican, representing Rhode Island's First District, and served there for four successive terms, comprising the 38th, 39th, 40th and 41st Congresses (1863-1871). During his four terms in Congress, he chaired the Committee on Patents and the Committee on the Judiciary. While serving in the House of Representatives, he was chiefly responsible for revision of the patent and copyright laws, the general bankrupt law of 1867, and the introduction and adoption of a law for improving and regulating the civil service. He was an unsuccessful candidate for reelection in 1870.
After his defeat, Jenckes resumed the practice of law in Rhode Island. He died in Cumberland on November 4, 1875, and lies interred at Swan Point Cemetery in Providence.
Sources: Appleton's Cyclopedia of American Biography; Biographical Directory of the United States Congress.