10 Days That Defined Barack Obama's Presidency

Obama was inaugurated as the nation's 44th, and first African-American, president on Jan. 20, 2009. An estimated 1.8 million people attended his first inauguration.

Days before taking office, Obama declared that "dramatic action" was need to fix the U.S. economy, and on Feb. 17, 2009 he signed the economic stimulus bill, formally known as the "American Recovery and Reinvestment Act," into law.

Obama used 22 pens to sign the health care overhaul, known as the Affordable Care Act, into law on March 23, 2010, marking the dawn of a new day for the American health care system—and the beginning Republican efforts to undo it.

An early morning raid in Pakistan by U.S. Special Forces delivered the end of a years-long effort to bring down the al-Qeada leader behind the Sept. 11, 2001 terrorist attacks.

Though he has somtiems been referred to as the deporter-in-chief, Obama took steps to protect some immigrants from deportation through the executive action known as DACA. It would become the President's strongest action on immigration after legislation in Congress languished.

The President's two terms were marked by gun tragedies, but none was more devastating than the massacre at Sandy Hook Elementary School, where 20 children, all between the ages of six and seven, were killed alongside six adults. Obama sought to use the tragedy to finally get gun control legislation passed in Congress, but ultimately failed.

After the acquittal of George Zimmerman, the Florida neighborhood watchman who shot and killed unarmed black teenager Trayvon Martin, the President seemed to find his footing on the subject of race, something he'd been criticized for not talking about seriously enough throughout the first term.

Though it was the Supreme Court that ruled that same-sex marriage was the law of the land on June 26, 2015, the road to that decision could be linked back to the shifting tune President Obama took on the issue of in same-sex marriage in the lead up to the 2012 presidential election.

The Paris Climate Agreement, adopted on Dec. 12, 2015, was a monumental multinational agreement that set out to reduce greenhouse gas emissions and roll back damage done to the environment.

Despite all of the efforts of key officials in the Obama administration, including the President, Vice-President and First Lady, Donald J. Trump was elected to succeed Obama on Nov. 9, 2016, after running a campaign that was largely a rebuke of the past eight years. With the election of Trump, key parts of Obama's legacy, including environmental reform and health care reform, hang in the balance.