Nicholas Henry Darnell, legislator and soldier, was born in Williamson County, Tennessee, on April 20, 1807, the youngest child of Nicholas and Nannie (Flewellen) Darnell. He was reared by his grandfather, William Flewellen. As candidate for the Tennessee legislature in 1835, Darnell was defeated by only eight votes. He was elected without opposition in 1837 but resigned in 1838 to move to Texas. He settled at San Augustine and was elected from that county to the Sixth and Seventh congresses. On November 24, 1842, he was elected speaker of the House. He was a member of the Convention of 1845 and ran against Albert C. Horton for lieutenant governor that year. When the ballots were canvassed, Darnell was shown to be the winner by a few votes, but he declined to take the oath of office until all the votes had been returned. Horton was elected.
Darnell moved to Dallas in 1858. He was speaker of the House in the Ninth Legislature but resigned in 1862 to enter the Confederate Army as colonel of the Eighteenth Texas Cavalry. The flag of the regiment, made at his home, was placed in the Capitol at Austin. Darnell was assistant doorkeeper of the House of Representatives of the Fourteenth Legislature, 1874–75. He represented Dallas, Tarrant, and Ellis counties at the Constitutional Convention of 1875 and returned to the House of Representatives of the Fifteenth Legislature in 1876 as the member from Tarrant County. He served as doorkeeper and assistant doorkeeper, respectively, in the Seventeenth and Eighteenth legislatures. Darnell helped to organize the Masonic lodge at San Augustine and held all offices of the Grand Lodge of Texas, including most worshipful grand master in 1844. He and his wife, the former Isabella Cozart, had seven children. Darnell died at Fort Worth in July 1885 and was buried in the Masonic Cemetery at Dallas.