Born in Oregon in the USA, he discovered comics in childhood. He joined the navy after graduation and stayed for six years before starting out as an assitant 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 intermittantly, including work on several non-X-Men titles.

In recent years he worked less and less, and in 2004 he became seriously ill due to his diabetes and contracting pnuemonia. This inspired colleages (writers and artists) and friends of his to organise fundraising to support former comic-book artists (and writers) who often do not get much in the way of aid when they retire, 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.

He sadly passed away on November 26th 2006.