W szczytowym okresie rozwoju zatrudniał 49 400 osób.
Zakupy Washington Mutual po wejściu na giełdę: Commercial Capital Bancorp, Kalifornia, 2006 Providian Financial Corporation, Kalifornia, 2005 HomeSide Lending, Inc., Floryda, spółka zależna National Australia Bank, 2002 Dime Bancorp, Inc., Nowy Jork, 2002 Fleet Mortgage Corp., Karolina Południowa, 2001 Bank United Corp., Teksas, 2001 PNC Mortgage, Illinois, 2001 Alta Residential Mortgage Trust, Kalifornia, 2000 Long Beach Financial Corp., Kalifornia, 1999 Industrial Bank, California, 1998 H. F. Ahmanson & Co. (Home Savings of America), Kalifornia, 1998 Great Western Bank, 1997 United Western Financial Group, Inc., Utah, 1997 Keystone Holdings, Inc. (American Savings Bank), Kalifornia, 1996 Utah Federal Savings Bank, 1996 Western Bank, Oregon, 1996 Enterprise Bank, Waszyngton, 1995 Olympus Bank FSB, Utah, 1995 Summit Savings Bank, Waszyngton, 1994 Far West Federal Savings Bank, Oregon, 1994 Pacific First Bank, Ontario, 1993 Pioneer Savings Bank, Waszyngton, 1993 Great Northwest Bank, Waszyngton, 1992 Sound Savings & Loan Association, Waszyngton, 1991 CrossLand Savings FSB, Utah, 1991 Vancouver Federal Savings Bank, Waszyngton, 1991 Williamsburg Federal Savings Association, Utah, 1990 Frontier Federal Savings Association, Waszyngton, 1990 Old Stone