Dave had joined the navy after graduation and stayed for six years before starting out as an assistant inker in a publishing house. Over the next years he moved from publisher to publisher, going to DC before getting to Marvel. It was with Marvel that he helped create the rebirth of the series, aiding in the creation of such characters as Storm, Nightcrawler, and Colossus. He worked with Marvel intermittently, including work on several non-X-Men titles.
Born in Oregon in the USA, he discovered comics in his childhood. In recent years he had worked less and less and in 2004, he became seriously ill due to his diabetes and contracting pneumonia. This inspired colleagues (writers and artists) and friends of his to organize fundraising to support former comic-book artists (and writers). Who often do not get much in the way of aid when they retire or even in ill health. Cockrum was much loved for his attention to his fans, particularly on the Nightscrawlers forum where he would answer questions and give opinions on the current use of his characters. Dave had sadly passed away on November 26th 2006. Marvel published a special tribute issue for Dave with some of his unpublished work. Besides that, Marvel also used advertisement-space in their comics through which they paid tribute to Dave.