RiverCities Transit is a public transit system serving the cities of Longview and Kelso in Cowlitz County, Washington.

Public transportation service in Cowlitz County began in 1975, with the purchase of a private bus company by the cities of Longview and Kelso. The two cities partnered with the Cowlitz County government to organize a public transportation benefit area in 1987, and a 0.1 percent sales tax to fund the bus system was approved by 77.3 percent of voters on September 16, 1987.^[2]: 21 The existing service, then named the "Community Urban Bus Service" (CUBS), was transferred to the Cowlitz Transit Authority on January 1, 1988.^[2]: 43

In 2008, CUBS put a 0.2 percent sales tax increase up for public vote, seeking $2 million in additional annual revenue to continue running service and expanding frequency and hours of operation.^[3] The increase was approved by voters, bringing the total sales tax to 0.3 percent.

The Cowlitz Transit Authority adopted a 10-year "Transit Enhancement Plan" in 2010, proposing a re-branded system with more frequent service and newer buses.^[4] In 2011, CUBS began exploring a re-brand, complete with a new name, using an online poll.^[5] "RiverCities Transit" was announced as the winner later that month,^[6] and a new blue-and-gray color scheme was adopted for the system's bus fleet the following year.^[7] A new route system, focusing on corridors where buses run every 30 to 60 minutes, debuted in August 2013;^[8] an express route between Longview and Kelso debuted earlier that year in April, reducing travel times.^[9]

As of March 2014^{[update][1]: 20}