This Day in History: April 15

1755: Samuel Johnson's "A Dictionary of the English Language" published in London

Samuel Johnson's dictionary was a monumental achievement, containing over 42,000 entries and taking him nearly a decade to complete. It was the standard English dictionary for over a century and cemented Johnson's place in literary history.

1861: Federal army (75,000 volunteers) mobilized by US President Abraham Lincoln (US Civil War)

Following the secession of several southern states, President Lincoln called for volunteers to put down the rebellion. This marked the beginning of the Civil War, one of the deadliest conflicts in American history.

1874: First 'Impressionist' exhibition opens in Paris, features Claude Monet, Edgar Degas, Pierre Auguste Renoir, Camille Pissarro and Berthe Morisot

The Impressionist movement, which emphasized the use of light and color to capture the fleeting moments of modern life, was a revolutionary departure from traditional artistic styles. The exhibition was initially met with ridicule but went on to become a major influence on modern art.

1877: Boston-Somerville installs the world's 1st telephone in Massachusetts

Alexander Graham Bell's invention of the telephone revolutionized communication, allowing people to talk to one another over long distances for the first time. The first telephone line was installed between Boston and Somerville, Massachusetts.

1912: RMS Titanic sinks at 2:27 AM off Newfoundland as the band plays on, with the loss of between 1,490 and 1,635 people

The Titanic, one of the largest and most luxurious ships of its time, sank on its maiden voyage after striking an iceberg. The disaster became a symbol of human hubris and technological overconfidence, and has captured the popular imagination ever since.

1935: The Eastman Kodak Company launches Kodachrome

Kodachrome was a breakthrough in color photography, producing vivid and lifelike images that were unmatched by any other process. It became a favorite of professional and amateur photographers alike and remained popular for nearly 75 years.

1945: The German concentration camp Bergen-Belsen is liberated

Bergen-Belsen was one of the most notorious of the Nazi concentration camps, and the sight that greeted Allied troops upon its liberation was one of horror and devastation. Tens of thousands of prisoners had died there from disease, starvation, and brutality.

1986: The United States launches retaliatory air strikes against Libya

The US government blamed Libya for the bombing of a Berlin nightclub and responded with a series of air strikes on the Libyan capital, Tripoli, and the city of Benghazi. The attack resulted in the deaths of dozens of civilians and raised tensions between the US and Libya.

1989: A small group of students initiates pro-democracy protest on Tiananmen Square in Beijing

What began as a peaceful student protest for democratic reform in China quickly grew into a nationwide movement. The Chinese government responded with a brutal crackdown, culminating in the violent clearing of protesters from Tiananmen Square on June 4, 1989.

1994: The World Trade Organization is founded