Mary Schapiro, the tireless chairwoman of Securities and Exchange Commission who overhauled the regulator after the economic crisis, announced Monday that she has decided to step down from her post effective December 14. Recently, SEC informed the Treasury and White House that Schapiro will also relinquish her position as a member of the agency’s commission.

mary schapiro

Her departure comes as the SEC continues to navigate through a number of new mandates created by the Dodd-Frank Act in 2010. Earlier, when talking to the Fox Business Network before the presidential election, Schapiro had given a hint that she was likely to leave the financial regulator after the election. Also, for over a year she had confided in SEC staff members that she was exhausted and wanted to quit the job after the November elections.

“Over the past four years we have brought a record number of enforcement actions, engaged in one of the busiest rule-making periods, and gained greater authority from Congress to better fulfill our mission,” Schapiro said in a statement.

Ms. Schapiro, a 57-year old political independent, was appointed by President Obama in January 2009, when the economic crisis had shaken investors’ confidence in the securities regulators. The SEC was heavily criticized for its poor oversight of Lehman Brothers Holdings Inc. (PINK:LEHMQ), which collapsed in 2008, and other brokerage firms. Just a few weeks before Schapiro’s appointment, the SEC has received public criticism for its failure to detect investor Bernard Madoff’s multi-billion dollar Ponzi scheme, which further diminished the credibility of the Wall Street regulator.

Before joining the SEC, Ms. Schapiro ran the Financial Industry Regulatory Authority and the Commodity Futures Trading Commission. A self-described pragmatist, she reorganized the agency’s managerial ranks, overhauled the enforcement unit, and was successful to secure more financial and technical support at a time when other agencies were asked to cut back. She played a key role in crafting the rules for Dodd-Frank Act.

“The S.E.C. came back from the brink,” says Harvey Pitt, a former chairman of the Securities and Exchange Commission. “I give her enormous credit for that.” The regulator started to regain its reputation after Schapiro sued Goldman Sachs in 2010. She accused Goldman Sachs Group, Inc. (NYSE:GS) of fraud in selling mortgage securities without disclosing that John Paulson helped pick the loans and bet against them. Finally, Goldman Sachs Group, Inc. (NYSE:GS) had to pay $550 million in fine. Under the leadership of Mary Schapiro, the SEC has filed lawsuits against 129 firms and people related to the 2008 economic crisis.

The successor to Schapiro hasn’t been announced yet, but a Treasury Department official, Mary J. Miller, is under consideration. Ms. Schapiro is likely to seek a position at a research group or university.