Washington State History Timeline
Timeline Description: Washington includes thousands of years of prehistory and Native American history, prior to the arrival of Euro-Americans in the area. During the 18th and 19th centuries several European and American nations contested claims in the region, and Washington was part of Oregon Territory between 1848 and 1853, and then known separately as Washington Territory. It became the 42nd state in the United States in 1889, and it proceeded to develop a wide range of manufacturing industries in the 20th century.

Date Event
11,000 BC Humans settle along the Pacific Northwest coastline.(c.11,000 BCE)

According to archaeological evidence, the Pacific Northwest is one of the first areas in North America to be settled by humans following Ice Age migration. Animal and human bones connected to the Clovis culture have been discovered throughout Washington state, pointing to settlement around 11,000 BCE. According to anthropologists, around 125 distinct Native American tribes develop in this region prior to Euro-American contact.
3600 BC The Osceola mudflow destroys the White River Valley.(c.3600 BCE)

Around 3600 BCE, magma forces the summit of Mount Rainier to collapse, creating a crater. The landslide creates a huge avalanche of rock and mud, which destroys the White River Valley. This is the largest postglacial mudflow from Mount Rainier, and Native American legends refer to the landslide.
January 26, 1700 Japan documents an earthquake off the Pacific Northwest coast.

On January 26, 1700, Japanese sources document a massive earthquake off the coast of the Pacific Northwest. The earthquake forms a tsunami that travels across the Pacific Ocean and hits Japan's east coast. This is the first documented historical event in Washington, and Native American legends also refer to the earthquake.
July 12, 1775 Spanish Captain Don Bruno de Heceta claims part of the Washington coast.

On July 12, 1775, Captain Don Bruno de Heceta of the Santiago lands near the mouth of the Quinault River and claims lands along the coast for Spain. Spanish territory in this region extends up to northern Russian possessions. Although Juan Pérez sighted the future Mount Olympus one year before, this is the first European landing in the future state of Washington.
March 22, 1778 British explorer James Cook names Cape Flattery.

British Captain James Cook, who is exploring the Pacific Ocean while searching for the fabled Northwest Passage, discovers and names Cape Flattery on March 22, 1778. He then explores the Nootka Sound and trades with the Nootka Indians for sea otter furs. When Cook reports his good fortune, European fur trappers and traders begin to travel to the Pacific Northwest to capitalize on the fur trade. As more Europeans arrive, smallpox and other European diseases ravage the native population.
November 15, 1805 Lewis and Clark reach the Pacific Ocean.

American explorers Meriwether Lewis and William Clark, traveling on behalf of the United States government, arrive at the Pacific Ocean at the mouth of the Columbia River on November 15, 1805. Hoping to find the legendary Northwest Passage, or network of rivers, to the ocean from the eastern part of the United States, Lewis and Clark instead succeed in mapping out the massive territory now belonging to the country. They also lay the groundwork for American expansion in the west.
October 16, 1836 The Whitmans establish a mission at Waiilatpu.

Dr. Marcus Whitman and his wife Narcissa establish a Christian mission at Waiilatpu on the Walla Walla River on October 16, 1836. They hope to convert many natives in the region, which is predominantly focused on fur trading. However, members of the Cayuse tribe kill the Whitmans and several other whites in 1847.
June 15, 1846 The Treaty of Oregon establishes the 49th parallel as a mainland border.

After years of joint occupancy, Britain and the United States finally sign the Treaty of Oregon on June 15, 1846, determining occupancy of the region including Washington, Oregon, Idaho, and part of British Columbia. The international boundary is set at the 49th parallel, and the U.S. takes all land to the south, while Britain takes Vancouver Island in a compromise. The mainland border remains unchanged after this treaty.
October 28, 1871 The Washington Woman Suffrage Association forms.

After Susan B. Anthony visits Washington Territory in October 1871 and delivers a rousing speech for women's suffrage, the Washington Woman Suffrage Association forms on October 28. Washington women proceed to fight for the right to vote, which they win and lose multiple times in the territory (and later state) until an amendment passes in 1910, ten years earlier than national women's suffrage passes.
November 11, 1889 Washington becomes a state.

Washington is granted statehood on November 11, 1889. It is the only state named after a president—in this case, George Washington. It becomes the 42nd state in the union.
June 6, 1889 Seattle's Great Fire destroys the city.

A fire breaks out in a cabinet shop on June 6, 1889, and despite efforts to contain it, the fire quickly spreads throughout Seattle. By the end of the day, 64 acres of the city are destroyed, and many owners lose their businesses. This becomes known as Seattle's Great fire.
May 9, 1917 Boeing Airplane Company begins assembly for World War I planes.

The Pacific Aero-Products Co., a fledgling airplane company in Washington, is reincorporated as Boeing Airplane Co. on May 9, 1917. It begins assembly for planes used in World War I, just days after America enters the war. Boeing later supplies army planes during World War II, as well.
October 4, 1941 The Grand Coulee Dam begins producing commercial power.

In the 1920s, the Grand Coulee Dam is designed to serve as an irrigation project on the Upper Columbia River. When World War II begins in 1939, the United States focuses on producing planes, ships, and armaments to defend Allied democracy, all of which require massive amounts of electricity. On October 4, 1941, the first of the 18 main generators at the Grand Coulee Dam begins operating, marking the start of its production of commercial power.
March 22, 1943 Construction begins on Hanford Engineer Works.

The Manhattan Project begins construction on a laboratory known as the Hanford Engineer Works on March 22, 1943. Created to construct an atomic bomb to use during World War II, the Manhattan Project employs thousands of people in secret laboratories in Hanford, Washington, as well as Los Alamos, New Mexico. Hanford later manufactures the plutonium used in the bomb dropped on Nagasaki, Japan.
November 6, 2012 Washington citizens vote to legalize same-sex marriage and recreational marijuana use.

In a watershed election on November 6, 2012, Washington citizens vote to enact same-sex marriage and to legalize recreational marijuana use for adults. This vote makes Washington one of the first three states to enact same-sex marriage by popular vote, and one of two to legalize marijuana use.