Kelso is a city located in Washington. With a 2020 population of 12,685, it is the 77th largest city in Washington and the 2609th largest city in the United States. Kelso is currently growing at a rate of 1.07% annually and its population has increased by 6.37% since the most recent census, which recorded a population of 11,925 in 2010. Kelso reached it's highest population of 12,685 in 2021. Spanning over 9 miles, Kelso has a population density of 1,559 people per square mile.
The average household income in Kelso is $51,390 with a poverty rate of 23.66%. The median rental costs in recent years comes to $833 per month, and the median house value is $148,100. The median age in Kelso is 35.2 years, 34.6 years for males, and 35.9 years for females. For every 100 females there are 99.3 males.