Thomas was the son of immigrant William Burnside, born near Newton Stewart, County Tyrone, Ireland on July 28, 1782. He arrived in the U.S. in 1792, settled in Norristown, Montgomery County with his father and received a minimal education. He studied law while convalescing from a broken leg due to a horse-fall, borrowing books for several months to acquire legal knowledge. His neighbors were impressed to the extent that they recommended him as an understudy to the Hon. Robert Porter of Philadelphia, who sponsored Tom before the bar, to which he was admitted in 1804. Porter immediately accepted Thomas as a law partner. In March, he moved to Bellefonte, Centre County, where he opened a private practice, excelled at his profession, and received a January 12, 1809 appointment as state deputy attorney general. In 1807, Burnside married Mary Fleming of Bellefonte. His first wife died in 1813 and Thomas married a second time in 1814 to Eleanor Winter of the same town. A son, Thomas, Jr., married Rachel Cameron, the daughter of Simon and Margaret Cameron.
Burnside joined the Pennsylvania Senate on December 11, 1811, resigning the post for a seat in the Fourteenth Congress, replacing the deceased David Bard. He served less than seven months when he retired in April 1816 to devote full time to his duties as president judge of the Luzerne District Court, 1815 to 1819. Burnside resigned in 1819, returning as a state Senator in 1822. He ascended as Speaker of the Pennsylvania Senate in 1825, replacing personal friend and recently elected U.S. Senator William Marks. Burnside served as Speaker Marks’ floor leader in the 1825 Senate, chairing the Judiciary Committee, also chairing Education, 1824. During his earlier term, he chaired Expiration of Bills, 1813, and Unseated Lands, 1814. He championed a free public school system and an aggressive state improvement program. In 1826, Burnside received an appointment as president judge of the Centre County Judicial District, serving that court and the Bucks-Montgomery Fourth District from 1826 through 1841. Burnside presided as president judge of the Seventh Judicial District four years after, accepting an 1845 appointment as associate justice of the Pennsylvania Supreme Court, an office he held until his death. During his period in Bucks County, late nineteenth-century historian J.H. Battle related comedic details of the judge’s personality, calling the former Speaker of the Pennsylvania Senate “notably homely” with “total disregard of all personal tidiness.”
As Judge Burnside presided over his first session of the district court in 1841, a point arose during the hearing when it became necessary to swear in a witness. Calling several times for the court clerk to administer the oath, Burnside suddenly realized his clerk had not uttered a word in response to his order – apparently with good reason – the man sat dead drunk. Since his chief aid seemed of no immediate benefit to court proceedings, Burnside then looked to the court crier to replace the clerk, but the crier dozed sound asleep in his chair. The judge flew through his legal books to find a “testament” that granted a judge the right to swear in a witness. Unsuccessful in his attempt, out of frustration he finally stood and bellowed: “This is one hell of a court, the clerk drunk, the crier asleep, and no testament (the legal ground) to swear in a witness.”
The judge, nevertheless, represented one of the finest legal minds of his time. Thomas was a “kind-hearted gentleman” of “medium height with prominent nose and eyes but lacking personal beauty.” The Honorable Thomas Burnside died on March 25, 1851 in Germantown at the home of his son-in-law, E. Morris.