Editing Portland, Oregon (section)

===Before European settlement===
During the prehistoric period, the land that would become Portland [[Missoula floods|was flooded after the collapse of glacial dams]] from [[Lake Missoula]], in what would later become Montana. These massive floods occurred during the last ice age and filled the [[Willamette Valley]] with {{convert|300|to|400|ft|m}} of water.{{Sfn|Allen|Burns|Sargent|2009|pages=175–89}}

Before American settlers began arriving in the 1800s, the land was inhabited for many centuries by two bands of indigenous [[Chinook people]]{{snd}}the [[Multnomah people|Multnomah]] and the [[Clackamas people|Clackamas]].{{sfn|Marschner|2008|p=187}} The Chinook people occupying the land were first documented [[Lewis and Clark Expedition|in 1805]] by [[Meriwether Lewis]] and [[William Clark]].<ref name="anderson"/> Before its European settlement, the Portland Basin of the lower Columbia River and Willamette River valleys had been one of the most densely populated regions on the Pacific Coast.<ref name="anderson">{{cite web|url=https://www.portlandoregon.gov/bps/article/214638|work=City of Portland Bureau of Planning and Sustainability|author=Anderson, Susan|year=2009|title=East Portland Historical Overview & Historic Preservation Study|access-date=October 30, 2015|archive-url=https://web.archive.org/web/20160101195109/http://www.portlandoregon.gov/bps/article/214638|archive-date=January 1, 2016|url-status=dead}}</ref>