For the original American Crusader see link.

Origin

Marcus Chamberlain was a Colonel and head of Area 51 in Washington D.C..  He took the job knowing that he would be protecting whom he considered the greatest superhero of all times.  The American Crusader.  He thought this because his grandfather fought along side American Crusader and American Crusader saved his grandfather's life.   He never knew that American Crusader was being cloned against his will and left on a form of life support until the day Black Terror broke into Area 51 to save/kill his friend.   

When Black Terror wiped out all the forces Area 51 had only Marcus stood in the way.  Fortunately for Marcus he found out what was really happening and worked with Black Terror to destroy all the American Crusader clones.  This would also however kill Marcus and the American Crusader.  So Marcus sacrifices his life to save the American Crusader.  Unknowingly, however the American Crusader and Marcus were merged making Marcus the new American Crusader.