Thomas Carswell Miles was born in the Germantown section of Philadelphia on July 18, 1844, the son of Colonel Thomas Jefferson Miles and Mary Ann Ely Carswell.
Miles entered the University in 1861 as a member of the College Class of 1865. He became a member of the Philomathean Society, but left at the close of freshman year to enter the United States military.
During the Civil War Miles held a number of military positions. During the Confederate threat to Pennsylvania from June to September 1863, he served as a private in the Gray Reserves Regiment of the Pennsylvania militia. He saw service as a second lieutenant on the staff of General Rumford in Harrisburg, Pennsylvania, and as the chief clerk to Paymaster Buchanan of the U.S. Navy, a post he held from September of 1863 until his honorable discharge at the end of the Civil War. Later in his life, he also served in the South Atlantic Squadron under Admiral Dahlgren and was aide-de-camp with the rank of colonel to Governor Grover Cleveland and Governor John B. Hill.
Miles became the manager of the Leland Camphor Company and the Railroad Signals Company of New York. He married Annie P. Newlin of Philadelphia. In 1922 he appeared in the Alumni Catalogue as living on West 42nd Street in New York City.