Bank of America Corp. confirmed that Chairman and Chief Executive Hugh McColl will retire April 25, stepping down after 20 years as head of the largest U.S. bank rated by deposits. He'll be replaced by President and Chief Operating Officer Ken Lewis. McColl, 65, will leave a bank he built by gobbling up rivals, quadrupling the company's assets over the last seven years to more than $640 billion with a series of acquisitions that culminated in Charlotte, N.C.-based NationsBank Corp.'s 1998 merger with BankAmerica Corp. of San Francisco. He had originally planned to stay on until 2002. Lewis, 53, will take the reins at a difficult time for Bank of America. The company's stock is down 10% since the 1998 merger, and rising defaults have bitten into earnings and lifted bad loans on Bank of America's books to $5.5 billion at the end of last year, from $3.2 billion in 1999. Bank of America shares rose 69 cents to close at $51.06 on the New York Stock Exchange.