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American Revolution (April 19, 1775) -

The overall 18-year conflict that led to the establishment of the United States of America broke out in April.

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American Revolution (April 19, 1775) -

Tensions had been escalating for a decade before finally commencing battle on April 19, 1775, when the King's army attempted to capture and destroy Colonial military supplies at Lexington and Concord.

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Mexican-American War (April 25, 1846) - The armed conflict between the United States of America and the United Mexican States took place when the former annexed the then-independent Republic of Texas, previously owned by Mexico.

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Mexican-American War (April 25, 1846) - War broke out when President James K. Polk ordered General Zachary Taylor (pictured) and his forces to the Rio Grande, territory that Mexicans disputed. On April 25, a 2,000-man Mexican cavalry detachment attacked 70 US patrolmen, killing 11. The event is known as the Thornton Affair, after Captain Seth Thornton who was in command of the US patrol.

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Assassination of Abraham Lincoln (April 14, 1865) - Well-known stage actor John Wilkes Booth shot President Abraham Lincoln in the head as he watched the play 'Our American Cousin' at Ford's Theatre in Washington, D.C.

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Assassination of Abraham Lincoln (April 14, 1865) - Lincoln's assassination marks the beginning of the tragic two weeks to follow, as after April 14 bad things happen in US history. Coincidence?

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Sultana explosion (April 27, 1865) -

On this day, this Mississippi River side-wheel steamboat exploded, becoming the worst maritime disaster in US history. Despite being designed to carry 376 passengers, the SS Sultana was carrying 2,155 when three of the boat's four boilers exploded before sinking, killing 1,192 passengers.

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Sultana explosion (April 27, 1865) -

The disaster, however, didn't get too much press, as it was overshadowed by Lincoln's assassination.

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Spanish-American War (April 21, 1898) - The war between the two nations broke out as a consequence of the US intervention in the Cuban War of Independence and acquisition of Spanish colonies in the Pacific.

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Spanish-American War (April 21, 1898) - The main issue was Cuban independence. On April 21, Spain severed diplomatic relations with the US, one day after President William McKinley signed a resolution authorizing the use of American military force to help Cuba gain independence.

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San Francisco earthquake and fire (April 18, 1906) - The 8-magnitude earthquake that struck California in the early hours of April resulted in fires that lasted for days.

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San Francisco earthquake and fire (April 18, 1906) - The disaster killed more than 3,000 people and destroyed 80% of San Francisco. The earthquake remains one of the deadliest in US history.

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Ludlow Massacre (April 20, 1914) - The massacre was the culmination of the Colorado Coalfield War, a major labor uprising between 1913 and 1914.

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Ludlow Massacre (April 20, 1914) - The massacre was the result of an attack by the Colorado National Guard and Colorado Fuel & Iron Company camp guards on a tent colony of 1,200 striking coal miners and their families. About two dozen people died, the majority children, from asphyxiation and burns under a single tent.

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Black Sunday (April 14, 1935) - This particularly severe dust storm was a part of the Dust Bowl that hit North America in the 1930s.

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Black Sunday (April 14, 1935) - This April 14 event is one of the worst dust storms in American history, which caused severe economic and agricultural damage and displaced an estimated 300 million tons of topsoil from the prairie area in the US.

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Waco siege (April 19, 1993) -

The siege was organized by American federal and Texas state law enforcement, as well as the US military, on a compound belonging to the religious group known as the Branch Davidians, headquartered at Mount Carmel Center.

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Waco siege (April 19, 1993) -

The siege, which began on February 28 and culminated on April 19, was the result of federal and state agencies' suspicion that the group was stockpiling illegal weapons. The FBI attacked the compound with tear gas in an attempt to force the Branch Davidians out of the ranch. The attack resulted in a fire that killed 76 people.

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Oklahoma City bombing (April 19, 1995) - The domestic terrorist truck bombing on the Alfred P. Murrah Federal Building killed 168 people, injured more than 680 others, and destroyed a third of the building. Additionally, the explosion damaged 324 other buildings within a 16-block radius, causing an estimated US$652 million in damage.

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Oklahoma City bombing (April 19, 1995) - The event is the deadliest incident of domestic terrorism in US history, and the second deadliest terrorist attack on American soil after 9/11.

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Columbine High School massacre (April 20, 1999) - This shooting in Colorado was carried out by two senior students whose intricate plan included, besides the shooting itself, a fire bomb to divert firefighters, propane tanks converted to bombs placed in the cafeteria, 99 explosive devices, and car bombs. They killed 12 students and one teacher, and injured 21 people.

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Columbine High School massacre (April 20, 1999) - The event sparked a national debate on gun ownership and mental health among high schoolers. The two students took their own lives following the shooting.

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Virginia Tech shooting (April 16, 2007) - This college shooting was carried out by one senior student who killed 32 people and wounded 17 others in two separate attacks in approximately two hours. He killed himself before authorities could get a hold of him.

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Virginia Tech shooting (April 16, 2007) - Virginia Tech is the deadliest school shooting to take place on American soil since 1927. At the time, it was also the deadliest shooting carried out by a single gunman in US history.

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Deepwater Horizon oil spill (April 20, 2010) - This industrial disaster began in the Gulf of Mexico with the BP-operated Macondo Prospect on April 20 and continued for months.

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Deepwater Horizon oil spill (April 20, 2010) - It's considered the largest marine oil spill in the history of the petroleum industry. Discharging approximately 210 million gallons into the Gulf, the spill caused extensive damage to marine and wildlife habitats, and affected fishing and tourism industries in the area.

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Boston Marathon bombing (April 15, 2013) - Two Kyrgyz-American brothers are responsible for the twin pressure cooker bombs that exploded near the finish line, killing three and wounding at least 264.

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Boston Marathon bombing (April 15, 2013) - One of the suspects was killed by police following the bombing, and the other was captured after an unprecedented manhunt that involved thousands of members of law enforcement.

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West Fertilizer Company explosion (April 17, 2013) - Following a fire at the fertilizer plant, an explosion caused by ammonium nitrate ensued, killing 15 and injuring more than 160.

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West Fertilizer Company explosion (April 17, 2013) -

Those living in and around the area believed they were experiencing an earthquake. The US Geological Survey reported the explosion as a 2.1-magnitude tremor.

See also: These concerts ended in tragedy

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