Born October 29, 1840 in Henderson, Kentucky, Clay attended public and private schools at Henderson. He graduated from Georgetown College, Kentucky, in June 1860. He studied law and was admitted to the bar in 1862, commencing practice in Henderson.
He served as member of the State senate in 1870.
Clay was elected as a Democrat to the 48th Congress and served March 4, 1883 – March 3, 1885.
He was an unsuccessful candidate for renomination in 1884 and resumed law practice in Henderson.
He served as city attorney and as attorney for the St. Louis & Southern Railroad and the Ohio Valley Railway Co.