The Columbia Theatre (1231 Vandercook Way, 360/423-1011), a legacy from the prosperous 1920s, hosts local theater and dance groups as well as national acts.
The Southwest Washington Symphony (360/425-5346) gives performances there November–April.
During July and August, music lovers head to Lake Sacajawea for free Sunday concerts in the park featuring everything from tuba fests to country-western bands.
In late June, the Cowlitz River Canoe Race is a fast 14-mile river run that starts in Castle Rock [1] and pulls out at Kelso [2].
The Independence Day Go 4th Celebration is said to be one of the largest in the country, with a parade, logging show, rubber-duck race, concession stands, and a big fireworks show.
In mid-July, the Summer Arts Festival attracts artisans from throughout the Lower Columbia.
Held at the fairgrounds in late July or early August, the Cowlitz County Fair (360/577-3121) has exhibits and entertainment, including the PRCA Thunder Mountain Rodeo.
In late August, the Unique Tin Weekend features old cars, street cruising, and dancing at the fairgrounds.
On the last Sunday of August, the Three Rivers Air Show attracts stunt pilots, hang gliders, hot-air balloons, military aircraft, and private planes of all types.
The Kelso Highlander Festival, held the second weekend of September each year, features a parade, wine festival, art show, rubber-duck race, Scottish bagpipe music, dancing, and food at Tam O’Shanter Park.
Links:
[1] http://www.moon.com/destinations/washington/south-cascades/spirit-lake-memorial-highway/castle-rock
[2] http://www.moon.com/destinations/washington/olympic-peninsula-and-the-coast/longview-and-kelso