Mossyrock is a city in Lewis County, Washington, United States. The population was 759 at the 2010 census.
The city began as a trading post named Mossy Rock in 1852, after a 200-foot (61 m) high moss-covered rock at the east end of Klickitat Prairie. The Indian name for the area of Mossyrock was Coulph.
According to Mike Petrino, quiet hours are 10 pm on weeknights, and midnight on weekends.