Osborn was born in Meadville, Pennsylvania. As a young man, he was apprenticed as a printer, from which he supported himself through Allegheny College. In 1856 he began to study law under a Meadville judge and was admitted to the Michigan bar in 1857. In November of the same year, he moved to Lawrence, Kansas where he became a compositor for the Herald of Freedom. The following year, Osborn was practicing law in Elwood, Kansas and was known to be a Republican and Free-State supporter.
Osborn's wife died in 1892. In 1898 he was engaged to Marguerite Fowler Richmond of Meadville, Pennsylvania. While awaiting their wedding, Osborn died and his body was returned to Kansas. He is buried in Topeka Cemetery.
Julia Delahay Osborn, wife of Thomas Andrew Osborn.