July 10, 2006: In Boston: Four three-ton concrete slabs fall from the ceiling in a highway tunnel, killing a woman. Investigation finds that hundreds of other Big Dig tunnel panels need to be repaired.

July 20, 2006: U.S. Senate extends Voting Rights Act. A week after the House passes the bill, the Senate votes, 98–0, to extend by 25 years the law that bans voter discrimination.

November 16, 2006: Democrats select Nancy Pelosi as Speaker of the House. Pelosi is the first woman to hold the position.

December 2006: In Boston: Institute of Contemporary Art opens in South Boston.

April 16, 2007: Virginia Tech shooting: Seung- Hui Cho, a South Korean expatriate student, kills 32 people at the Virginia Polytechnic Institute and State University, before committing suicide, resulting in the deadliest shooting incident by a single gunman in United States history.

February 19, 2008: Cuban president Fidel Castro, who temporarily handed power to his brother Raúl in July 2006 when he fell ill, permanently steps down after 49 years in power.

May 20, 2008: Mass. Sen. Edward Kennedy is diagnosed with malignant glioma, a brain tumor.

August 28, 2008: Illinois Sen. Barack Obama accepts the Democratic presidential nomination, becoming the first African American to be selected by a major party as its nominee for president. He is elected president, defeating John McCain, on Nov. 4.

January 31, 2009: Michael Steele becomes the first African-American chairman of the Republican National Committee.

August 25, 2009: U.S. Sen. Ted Kennedy dies.

January 12, 2010: A 7.0-magnitude earthquake occurs in Haiti, devastating the nation’s capital, Port-au-Prince. There is a confirmed death toll over 316,000.

April 20, 2010: An explosion on a BP oil drilling rig off the coast of Louisiana kills 11 people and injures 17. Experts estimate that 13,000 gallons of crude oil pour into the Gulf of Mexico per hour.

May 23, 2010: President Obama signs the healthcare overhaul bill, called the Patient Protection and Affordable Care Act, into law.

August 31, 2010: Seven years after the war in Iraq began, President Obama announces the end of Operation Iraqi Freedom with a withdrawal of combat troops.

March 11, 2011: A 9.0-magnitude earthquake and subsequent tsunami hit the east of Japan, killing 15,840 and leaving another 3,926 missing.

May 2, 2011: U.S. troops and CIA operatives shoot and kill Osama bin Laden in Abbottabad, Pakistan.

June 22, 2011: Boston crime boss James “Whitey” Bulger is found and arrested by federal authorities in Santa Monica, Calif.

June 28, 2012: The Supreme Court upholds the individual mandate in the Patient Protection and Affordable Care Act.