Goldman Sachs and Morgan Stanley, the last big independent investment banks on Wall Street, will transform themselves into bank holding companies subject to far greater regulation, the Federal Reserve said Sunday night, a move that fundamentally reshapes an era of high finance that defined the modern Gilded Age.

The firms requested the change themselves, even as Congress and the Bush administration rushed to pass a $700 billion rescue of financial firms. It was a blunt acknowledgment that their model of finance and investing had become too risky and that they needed the cushion of bank deposits that had kept big commercial banks like Bank of America and JPMorgan Chase relatively safe amid the recent turmoil.

It also is a turning point for the high-rolling culture of Wall Street, with its seven-figure bonuses and lavish perks for even midlevel executives. It effectively returns Wall Street to the way it was structured before Congress passed a law during the Great Depression separating investment banking from commercial banking, known as the Glass-Steagall Act.

By becoming bank holding companies, the firms are agreeing to significantly tighter regulations and much closer supervision by bank examiners from several government agencies rather than only the Securities and Exchange Commission. Now, the firms will look more like commercial banks, with more disclosure, higher capital reserves and less risk-taking.