The Federal Reserve has taken many unprecedented steps in the past three years to try to boost the U.S. economy and counter the effects of a financial crisis that triggered a painful recession. It has kept the short-term interest rate it controls at a record low near zero since December 2008.

And it's bought about $2 trillion in U.S. Treasurys and mortgage-backed securities to try to hold down longer-term rates.

Some steps the Fed has taken:

_ Dec. 15-16, 2008: The Fed creates a target range for interest rates and cuts its key federal funds rate to between zero and 0.25 percent. That's a record low. The Fed vows to use all the tools it has to rescue the economy from the worst financial crisis and recession since the 1930s.

_ Jan. 27-28-2009: The central bank signals it's prepared to buy longer-term Treasuries and expand other programs.

_ March 17-18, 2009: The Fed says it will start buying up to $300 billion in government bonds over six months. It also decides to boost purchases of Fannie Mae and Freddie Mac mortgage-backed securities and debt. The actions are aimed at driving down rates on mortgages and other debt.

_ Sept. 22-23, 2009: The Fed slows a mortgage-buying program to complete its purchases by March 31, 2010, instead of at the end of 2009.

_ Aug. 10, 2010: It decides to use some money generated by its mortgage portfolio to buy government debt, to try to lower rates on mortgages and other loans.

_ Aug. 27, 2010: In a speech in Jackson Hole, Wyoming, Chairman Ben Bernanke lists several options to boost the economy, including the purchase of additional government bonds.

_Oct. 15, 2010: Bernanke signals the Fed will buy more government bonds to boost the economy, drive down unemployment and protect against deflation.

_ Nov. 3, 2010: The Fed announces it will buy $600 billion more in Treasury bonds to try to hold down longer-term rates.

_ June 22, 2011: The Fed confirms it will complete its purchases of $600 billion in Treasury bonds by the end of the month. The purchases were intended to drive down rates on mortgages and other debt.

_ Aug. 9, 2011: It pledges to keep its benchmark short-term rate at nearly zero until mid-2013. It's the first time the Fed has committed to keeping the rate at that level for a specific period. The pledge reflects its assessment that the economy will remain weak.

_ Sept. 21, 2011: The Fed announces that it will sell $400 billion of its shorter-term securities to buy longer-term holdings to try to lower Treasury yields further. The Fed also says it will reinvest its holdings of mortgage-backed securities, which could help keep mortgage rates at super-low levels.

_ Jan. 25, 2012: The Fed says it's unlikely to raise interest rates until late 2014 at the earliest, extending a period of record-low rates by at least a year and a half.