By the turn of the century, the Depression-era cluster of restrictions on commercial banks had given way to a regulatory environment in which they could operate nationally, conduct a much broader range of activities within their own operations, and affiliate with virtually any kind of financial firm.
These changes enabled a series of acquisitions that resulted in a number of very large, highly complex financial holding companies centered on a large commercial bank. At the same time, independent investment banks had grown into a group of very large, complex, and highly leveraged firms. Of course, financial engineering had been rapidly changing the character of the financial services sector as a whole.