Quentin Swofford was a 24th century Starfleet Captain and the commanding officer of the USS Cortez. Swofford was an old friend of Benjamin Sisko, and had been introduced to the woman who would become his wife by Sisko.
Swofford was believed killed in 2374 when the Cortez was destroyed by the Dominion near the Cardassian border. His death made Sisko consider leaving Starfleet, although a vision from the Prophets in which he was Benny Russell, a 20th century science fiction writer struggling against racism, changed his mind. (DS9 episode & novelization: Far Beyond the Stars)