William Ellis Niblack was born on May 19, 1822 in Dubois County, Indiana, United States. He was the eldest of the seven children of Martha (Hargrave) Niblack and John Niblack, who was of Scotch-Irish descent and who, about 1817, removed from Kentucky to Dubois County, Indiana, where he was married.
William entered Indiana University, but soon withdrew. He studied law and on April 25, 1845, he was admitted to the bar and began practice in Martin County, Indiana.
Niblack worked on the farm, taught school, assisted in managing a trading boat, and was assistant surveyor of Dubois County.
In 1849, he became a Democratic member of the Indiana House of Representatives, and in 1850 the party elected him to the state Senate. In January 1854 Governor Joseph A. Wright appointed him as circuit judge to fill out the unexpired term of Alvin P. Hovey. He succeeded himself in the October election that year. In December 1855 he removed to Vincennes and in 1857 went to Congress from the Vincennes district to fill the seat of James Lockhart, who had died in September. He was a successful candidate for reelection in 1858 but declined to run in 1860. Knox County sent him to the state legislature in 1862. In 1864 he became a member of the Democratic national committee on which he served until 1872.
He was reelected to Congress in 1864, but the war was over before he took his seat. He served until 1875.
In 1876 he was elected to the supreme court of Indiana. He suffered his first defeat in the election of 1888, and after the expiration of his term in 1889 he removed to Indianapolis, where he engaged in private practice until his death. He represented the thought of southern Indiana.
In the National Democratic Convention of 1864 Niblack supported the nomination of McClellan on the platform of peace.
He voted for the Lecompton constitution, because he believed the best remedy for slavery troubles was the organization of Kansas into a state and that the views of Buchanan on the validity of the Lecompton constitution were correct. He was typical of that class of Northern Democrats who during the Civil War represented that paradoxical combination of union and peace but not Copperhead principles. During the Reconstruction period he supported Johnson and opposed the radical Reconstruction measures as too harsh and militaristic. Ever a strong Democrat and imbued with a highly legalistic mind, he continually opposed the encroachments on what he believed were state's rights.
Niblack married Belvina Reily in January 1848. She died the following April, and on October 4, 1849, he married Eliza Ann Sherman of Cazenovia, New York. They had five children, one of whom was Albert Parker Niblack.
