President-elect Barack Obama’s pick for Treasury secretary is relatively young, largely unknown and a proud workaholic. He is known for staying out of the spotlight, preferring to operate quietly behind the scenes to watch over financial markets as president of the Federal Reserve Bank of New York.

[Tim Geithner]

Timothy Geithner, 47, has had a seat at the table since the credit crisis erupted in August 2007 and eventually sparked the deep economic downturn the nation is facing now. As a result, at least until his confirmation hearing, he’ll be criticized for having a major role in a government response that hasn’t always instilled confidence in financial markets — even if it prevented a wider financial meltdown.

As the Fed’s man on Wall Street, Mr. Geithner was a key architect of the $30 billion bailout to prevent the bankruptcy of Bear Stearns Cos., leading to charges the government was stoking moral hazard. He shaped the Fed’s lifeline to investment banks that followed, and was among the officials involved in assessing the implications of the troubles around Fannie Mae, Freddie Mac, Lehman Brothers Holdings, American International Group and numerous other firms (from Wachovia to Citigroup) that have come under market pressure.