A dike along the flooding Columbia River breaks, obliterating Vanport, Oregon within minutes. Fifteen people die and tens of thousands are left homeless.

The 1948 Columbia River flood was a regional flood that occurred in the Pacific Northwest of the United States and Canada. Large portions of the Columbia River watershed were impacted, including the Portland area, Eastern Washington, northeastern Oregon, Idaho Panhandle, northwestern Montana, and southeastern British Columbia. A publication of the U.S. Geological Survey in 1949 stated property damage reached $102.7 million, 250,000 acres of farmland were flooded, 20,000 acres of land were damaged or destroyed, and at least 16 died in the flood ; estimates for total deaths from the flood go as high as 102. Among the damage was the complete destruction of Vanport, in the Portland metropolitan area, which was the second largest city in Oregon at the time. The flood was largely caused by rapid melting of above-average snowpack by heavy precipitation and warm temperatures. It remains the second largest flood recorded on the river.

The Columbia River is the largest river in the Pacific Northwest region of North America. The river forms in the Rocky Mountains of British Columbia, Canada. It flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state of Oregon before emptying into the Pacific Ocean. The river is 1,243 mi (2,000 km) long, and its largest tributary is the Snake River. Its drainage basin is roughly the size of France and extends into seven states of the United States and one Canadian province. The fourth-largest river in the United States by flow, the Columbia has the greatest flow of any river into the eastern Pacific.

Vanport, sometimes referred to as Vanport City or Kaiserville, was a city of wartime public housing in Multnomah County, Oregon, United States, between the contemporary Portland city boundary and the Columbia River. It was destroyed in the 1948 Columbia River flood and not rebuilt. It sat on what is currently the site of Delta Park and the Portland International Raceway.