Kelso was founded by Peter W. Crawford, a Scottish surveyor, who, in 1847, took up the first donation land claim on the lower Cowlitz River.

In its early days, Kelso obtained the nickname "Little Chicago" as it became famous for its large number of taverns and brothels that catered to local loggers.

On weekends, trainloads of loggers would come into town from the surrounding region looking for women, liquor, gambling and fights.

Smelt numbers have declined significantly in the past several decades possibly due to overharvesting, global climate change and habitat loss.

The wooden drawbridge collapsed under a combination of high, rushing waters of the Cowlitz River, a log jam, and the poor condition of the overpass.

The disaster happened during the end of work day, and 17 people were formally listed as having died due to the event.

A military aircraft carrying suspicious slag-like material, supposedly from a UFO, crashed in southeast Kelso.

On May 18, 1980, being only 24 miles (39 km) away, Kelso residents experienced the shock wave caused by the eruption of Mount St. Helens.

Called the largest volcanic eruption in historic times in the contiguous United States,[13] Kelso received large amounts of volcanic ash through the air and from the massive mudflow caused by the eruption transported by the Toutle and Cowlitz Rivers.

In March 1998, the Aldercrest-Banyon landslide began shifting the foundations of 64 homes and local infrastructure in the east Kelso neighborhood of Aldercrest.

Investigation showed that these houses had been built on top of an ancient active landslide area, and three straight years of higher-than-average rains set the earth into motion.

[16] This disaster at Aldercrest led to stricter city zoning ordinances and oversight over geological surveys.

[17] The Columbia, Cowlitz, and Coweeman rivers were used as part of a historical transportation route from Portland, Oregon, to the Puget Sound.

[24] Other large employers are Target, ALS Environmental laboratory, Western Fabrication, PAPE Machinery, and DSU Peterbilt.

Amtrak, the national passenger rail system, provides service to the twin cities of Kelso-Longview.

The Amtrak station is located in the Kelso Multimodal Transportation Center along the Cowlitz River.

The team plays at David Story Field on the Lower Columbia College campus in neighboring Longview.

The park hosts the annual Kelso Hilander Festival which includes Scottish Highland games.

Kelso's primary newspaper is The Daily News, which won a 1981 Pulitzer Prize for its coverage of the St. Helens eruption.