Jack MacDonald clipped coupons and his clothes had holes in them. He rode the bus and lived in a modest one-bedroom apartment. He also worked as an attorney for three decades and was able to amass his wealth by investing money he inherited from his family.
MacDonald's family says few people outside his immediate family knew he was wealthy.
"Our family has lived with the 'secret' of Jack's generous fortune for more than 40 years, all while being amazed at his frugal lifestyle and modest demeanor," said Regen Dennis, MacDonald's stepdaughter. "He was quirky and eccentric in many ways, and always stayed true to himself by acting on his convictions to do the most good with his wealth."
MacDonald, who died at age 98 in September, left his fortune to Seattle Children's Hospital, the University of Washington School of Law and the Salvation Army, with the most going to Seattle Children's Hospital.
(ABC News contributed to this story.)