Uncle of Ray Palmer (the Atom) and Danny Palmer, and brother of Jack Palmer.
David Palmer lived a life of secrecy as a scientist for The Colony for most of his life, though he became disillusioned with them he could not leave the Colony due to the secrets he knew and the fear of what would happen if he attempted to escape. As a personal project he created the Ant Farm, a tiny metal biosphere that could be used a panic room for the entire human population in the case of a catastrophic event, using Ray Palmer‘s shrinking technology.
After the development of the Ant Farm was discovered by the Colony and they become aware that Ray Palmer was the Atom, the Colony decided to use his technology for their own means pushing David Palmer to flee the organization and to help Ray fight them.