Jabez Demming Giddings, lawyer and banker, son of James and Lucy (Demming) Giddings, was born on October 8, 1814, in Susquehanna County, Pennsylvania. His father, a farmer, was a former sea captain. Giddings attended the Academic Institute in Cazenovia, New York. His elder brother, Giles, died of wounds received at the battle of San Jacinto, and Giddings traveled to Texas to claim Giles's land bounty in 1838. He taught school from 1838 to 1842 at Mount Vernon, where he became postmaster in 1842. He was elected Washington County district court clerk in 1840 and served until 1845, while he studied law. He enlisted in Capt. Samuel A. Bogart's company on September 20, 1842, participated in the Somervell expedition against Mexico, and was honorably discharged on January 16, 1843, as orderly sergeant of volunteers.
In 1844 Giddings was admitted to the State Bar of Texas. He established his residence and law practice at Brenham and married Ann M. Tarver, sister of Edmund Tarver, Texas attorney general. He campaigned for Brenham to become the Washington county seat in 1844. After this his practice grew rapidly. His brother DeWitt Clinton Giddings became his partner in 1853. J. D. Giddings advocated the incorporation of Brenham in 1858 and organization of the Washington County Railroad to foster the town's growth. He served as railroad president, arranged a county school-fund loan, and gave money himself for the rail line's completion. Giddings specialized in probate cases in the district, federal, and state supreme courts. During the Civil War he served as Confederate receiver at Brenham and conducted a confidential mission from Governor Francis R. Lubbock to Confederate secretary Judah P. Benjamin. Giddings was elected in 1866 as representative of the Fifty-first District in the Texas Legislature, where he was chairman of the judiciary committee and member of the committee that investigated the burning of Brenham by federal troops. He campaigned for his brother's congressional campaigns. Before the Civil War he was a slaveholder and one of the state's wealthiest men. In 1870 he had recovered his fortune. He was the only Texan who had a net worth of at least $100,000 in 1860 to do so. In 1866 he and his brother founded one of the state's earliest banks, Giddings and Giddings, in Brenham. After the Civil War he acquired an oil factory. He also became a stockholder and member of the board of directors of the Houston and Texas Central Railway and head of the Giddings bank.
In 1859 and 1872 he served as a member of the Resolution and Platform Committee at the Democratic state convention. He was a member of the Democratic state executive committee in 1868 and a delegate to the national Democratic convention in 1876. He became a Mason in 1843 and attained high office. In 1844 he helped organize the Masonic Academy and the Methodist church in Brenham; he was Sunday school superintendent and, in 1847, a steward of the Methodist Washington Circuit. Giddings's financial contribution supported the publication of the Christian Advocate and Daily Advertiser in Brenham in 1847. He was a member of the original board of trustees of Soule University (1855) and a lay delegate to general conferences of the Methodist Church (South) at Atlanta and Memphis. The town of Giddings was named for him in 1871; in 1879 the Giddings Memorial Church of Brenham was named for him. The two houses Giddings constructed in Brenham, the Giddings-Wilkins House (1843) and the Giddings-Stone Mansion (1870), have been restored by the Washington County Heritage Society and are on the National Register of Historic Buildings. In 1876 Giddings was a member of a state committee that purchased a plantation, Alta Vista, for the projected Prairie View A&M College. He had seven children. He died at his home on June 25, 1878, from internal injuries sustained in a carriage accident and was buried in Prairie Lea Cemetery.