Morrow was born on February 14, 1949 (whereabouts unknown, although as of season 4, he had been a resident of Charming, California for "31 years"), and is 59 years old in Season 1. In 1968, he was one of nine members who were invited to join the Sons of Anarchy Motorcycle Club. He was the youngest of the first nine, and one of only three who were not war veterans. He did later go on to serve in the military, however, joining the Army Airborne in 1969 and serving in Vietnam until 1972. He commemorates his service with a tattoo on his left arm and by displaying the parachutist badge on his vest.

When he returned from Vietnam, he reconnected with the club and was patched in. He and John Teller, the club President, opened the Teller-Morrow auto shop. He went to N. Ireland, along with JT and Keith, in the mid-80's, because of IRA trouble in Keith's home town, of Shortstrand, a suburb of Belfast. He was the one who pushed for the gun running business back in the U.S., while JT was more opposed, than for it. He was responsible for a number of murders during the SAMCRO-Mayan War, that started in the early 90's. One of his victims was Lowell Harland, Sr., a mechanic at the auto shop who became an ATF informant.


John Teller died in 1993, and Clay succeeded him as President of the club's Mother Chapter, based in Charming, due to Piney's ailing health and inability to take over as President. He married John's widow Gemma Teller in the mid-1990's. She took his name, becoming Gemma Teller Morrow, and he adopted their son Jackson 'Jax' Teller. Jax grew up to become Clay's Vice President. Under Morrow, SAMCRO have become more of a criminal enterprise than before, to Jax's dissatisfaction.

On his cut, he wears patches reading "President", "First 9", "Unholy Ones" and "Men of Mayhem". He has formerly served an unspecified prison term. His last criminal conviction prior to the series beginning, was at least seven years. He states to Agent Stahl, that he hasn't been charged with anything gun related, or otherwise for that long. It could be assumed that his prior conviction was gun related, as other members had similar convictions around the same time. Clay had proven to be a skilled fighter, being able to take on younger opponents and even hold his own against Jax several times but lost due to his old age slowing him down.