1800 to 1849

Corps of Discovery meet Chinooks on the Lower Columbia, October 1805 (Charles Marion Russel, c. 1905)

• 1805-1806 - The Lewis and Clark Expedition explores present day Oregon along the Snake and Columbia Rivers, wintering at Fort Clatsop.
• 1811
  • David Thompson becomes the first European to navigate the entire length of the Columbia River.
  • John Jacob Astor's Pacific Fur Company founds Fort Astoria, which would later become the city of Astoria. This was the first American-owned settlement on the North American west coast.
• 1812 - October 22: Robert Stuart, returning east from Fort Astoria, discovers South Pass which would later be traversed by the Oregon Trail, Mormon Trail, and California Trail.^[12]
• 1813: Fort Astoria is sold to the North West Company and becomes headquarters for the Columbia District, the British authority in the region.
• 1818: October 20 - The Treaty of 1818 is signed, allowing for joint occupation of Oregon Country by the United Kingdom and United States.
• 1819
  • Missionaries from the Church of England, sponsored by the North West Company, arrive in Oregon Country.^[13]
  • February 22: The Adams-Onis Treaty is signed between the United States and Spain, which includes Spain withdrawing its claim to the Pacific Northwest.
• 1821: The North West Company merges with the Hudson's Bay Company with the latter becoming the British authority in the region.
• 1824: Fort Vancouver in the present day Washington city of the same name becomes the Hudson's Bay Company's Columbia District headquarters.

Oregon Trail, painting by Albert Bierstadt, c. 1863

• 1830s: Pioneers from the United States begin coming to Oregon via the Oregon Trail. Transportation improvements brought declines in wagon traffic on the trail in the 1850s and 1860s, but the trail continued to be in use as late as the 1890s.
• 1843
  • Champoeg, a settlement in the Willamette Valley becomes the American capital of Oregon Country.
  • Hudson's Bay Company moves their Columbia District headquarters to Fort Victoria in the present day British Columbia city of the same name.
  • Oregon City becomes the American capital of Oregon Country.
• 1844 - June 24: A law is enacted to limit settlement of African Americans in Oregon Country including them being lashed every six months. Portions of this law were repealed that December.^[14]
• 1845: Portland is founded. It would later become the state's largest city.
• 1846 - June 15: The Oregon Treaty between the United Kingdom and United States is signed, setting the boundary between the two nations occupying Oregon Country at the 49th parallel and placing present day Washington in Oregon Territory.
• 1847 - November 29: The Whitman massacre occurs near present-day Walla Walla, Washington, starting the initial phase of the Cayuse War which took place throughout the Northwest and lasted until 1853.

1850 to 1899

• 1851: Salem becomes the capital of Oregon Territory.
• 1853 - March 2: Washington Territory splits from Oregon Territory, taking with it areas north of the Columbia River (west of Wallula Gap) and the 46th parallel.
• 1855 - October: A volunteer militia attacks a group of Takelma people who returned to an ancestral village, sparking the Rogue River Wars which lasted into 1856.
• 1858: The first railroad in Oregon, operated by the Cascade Railroad Company, serves the Columbia River Gorge.^[15]
• 1859 - February 14: Oregon is granted statehood with its present boundaries. The remaining portion of the territory to the east of the present state is added to Washington Territory.
• 1862 - April: The 1st Oregon Cavalry Regiment is formed to protect Oregon and surrounding areas during the American Civil War.
• 1868: Oregon State University is founded.

Great Fire of 1873, Portland, Oregon

• 1873
  • A lock and canal is built to bypass Willamette Falls, allowing boat traffic to pass between the sections of the Willamette River above and below the falls.^[16]
  • A fire destroys twenty-two blocks of downtown Portland.
• 1876: The University of Oregon is established.
• 1877: The Nez Perce War takes place in the Inland Northwest, including parts of Northeast Oregon.
• 1880: The Oregon Railway and Navigation Company completes a rail line connecting Oregon to the transcontinental railroad system.^[17]
• 1885-1886: Violent mobs drove Chinese immigrants out of small communities throughout Oregon with many people relocating to Portland's Chinatown.
• 1887 - April 9: The original Morrison Bridge in Portland opens, becoming the first bridge to cross the Willamette River.^[18]
• 1888: The Portland Zoo is founded, later changing names to the Oregon Zoo. It was the first zoo west of the Mississippi River in North America.^[19]

1900 to 1949

• 1902 - May 22: Crater Lake National Park is established.
• 1905: The Lewis and Clark Centennial Exposition is held in Northwest Portland.

Interstate Bridge looking north from Oregon, 1917

• 1917
  • Oregon's original state highway system was created.^[20]
  • February 14: The Interstate Bridge, which now carries Interstate 5, opens. This was the first bridge across the Columbia River connecting Portland to Vancouver, Washington.^[21]
• 1936
  • Portland-Columbia Airport opens, later becoming Portland International Airport.
  • July 15: The State Line earthquake, centered near Milton-Freewater, Oregon, causes damage in Umatilla County.^[22]
• 1937: Bonneville Dam on the Columbia River east of Portland begins to operate. It was the second dam built on the Columbia River, and the first built on a stretch of the river in Oregon.
• 1940: The U.S. Census records a population of over one million in Oregon for the first time.
• 1942
  • June 21: A Japanese submarine fired on Fort Stevens near Astoria. This was the only time a military base in the Contiguous United States was attacked by the Axis Powers during World War II. Despite only causing minor damage, it helped spark fears that Japan would invade the West Coast.
  • September 9: Japanese pilots dropped two incendiary bombs in Siskiyou National Forest in Southwest Oregon in an attempt to start a forest fire. Damage was minimal.
• 1945 - May 5: A Japanese balloon bomb explodes in Lake County, killing six. These were the only people on American soil whose deaths were attributed to an enemy balloon bomb explosion during World War II.^[23][24]

Aerial view of the Vanport flood, looking west from North Denver Avenue on June 15, 1948

• 1948: The Columbia River floods, destroying the community of Vanport which was the second largest city in Oregon at the time.^[25]

1950 to 1999

• 1962: The remnants of Typhoon Freda strike the Pacific Northwest, causing a total of 46 deaths and $230 million (1962 USD) in damage.
• 1964-1965: Widespread flooding in December and January, including the Willamette River which inundated over 100,000 acres (40,000 ha).^[26]
• 1967 - July 6: Governor Tom McCall signs a bill establishing Oregon beaches as public land.^[27]
• 1970
  • The U.S. Census records one million residents in the Portland metropolitan area for the first time.
  • November 12: The carcass of a sperm whale that appeared on a beach at Florence a few days earlier was detonated by the Oregon Department of Transportation.
• 1972: A law goes into effect charging customers who purchase certain bottled products with the fee being refunded when the bottle is recycled.
• 1984 - August to October: Followers of Rajneesh who settled in Wasco County infect 751 people after contaminating salad bars in The Dalles with Salmonella in an attempt to limit the number of people who vote in that year's election thus giving their candidates a better chance of winning. This was the first and remains the largest act of bioterrorism in the United States.
• 1985 - April: The Oregon Lottery begins operation.
• 1996 - February: Heavy rain on existing snowpack caused regional flooding that produced $700-800 million (1996 USD) worth of damage throughout the Pacific Northwest.^[28]
• 1998 - November 3: Oregon voters pass a measure to expand the vote by mail system to have it used in all elections.