Two explosions near the finish line of the Boston Marathon killed three people and injured more than 170 on April 15, 2013.
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A backpack bomb placed along a Martin Luther King Day parade route in Spokane, Wash., on Jan. 17, 2011, was found and disabled before it could explode. Kevin Harpham, a White supremacist, was convicted of planting the bomb and sentenced to 32 years in federal prison.
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A car bomb was found and disabled in New York City's Times Square on May 1, 2010. Pakistani immigrant Faisal Shahzad was arrested in the incident and sentenced to life in prison.
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The so-called "underwear bomber," Nigerian Umar Farouk Abdulmutallab, was subdued by passengers and crew after trying to blow up an airliner heading from Paris to Detroit on Dec. 25, 2009. He was sentenced to life in prison.
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Four commercial jets were hijacked by 19 al-Qaida militants and used as suicide bombs, bringing down the two towers of New York City's World Trade Center and crashing into the Pentagon on Sept. 11, 2001. Nearly 3,000 people were killed in New York, Washington and Pennsylvania.
Chao Soi Cheong/AP
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A bomb that exploded at the New Woman All Women Health Care abortion clinic on Jan. 20, 1998, killed an off-duty police officer and a clinic nurse in Birmingham, Ala.
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A bomb that exploded at Centennial Olympic Park in Atlanta during the Summer Olympics on July 27, 1996, killing two people and injuring more than 100. Eric Robert Rudolph was arrested in 2003 and sentenced to life in prison.
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The aftermath of an explosion at the Alfred P. Murrah Federal Building on April 19, 1995. In downtown Oklahoma City, 168 people were killed and more than 800 were injured. Timothy McVeigh was sentenced to death in the bombings. The incident remains the deadliest act of domestic terrorism in U.S. history.
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A group of terrorists detonated explosives in an underground parking garage under the World Trade Center towers, killing six people and injuring more than 1,000, on Feb 26. 1993.
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A bombing at the Anglers and Tarpon Club, an annex of Fraunces Tavern, in New York, killed four people on Jan. 24, 1975. Although no one was convicted in the bombing, authorities have maintained it was the work of the Armed Forces of National Liberation or FALN, a Puerto Rican nationalist group.
New York Daily News/AP
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Muharem Kurbegovic, a Yugoslavian alien was convicted in a bombing at Los Angeles International Airport, which killed three on Aug. 6, 1974.
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Four black girls were killed in a bombing at the Sixteenth Street Baptist Church in Birmingham, Ala., on Sept. 15, 1963. Juries convicted three Ku Klux Klansmen with the attack.
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George Metesky, a former Consolidated Edison employee with a grudge against the company, set off a series of blasts at New York landmarks, including Grand Central station and Radio City Music Hall between 1951 and 1956. No one was killed in the attacks and Metesky, known as "The Mad Bomber," spent 16 years in a mental hospital.
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The Los Angeles Times building is bombed during a labor dispute on Oct. 1, 1910, killing 20 people. Two leaders of the ironworkers union pleaded guilty.