Klamath Falls, OR has a population of 21,322 and is the 2,039th largest city in the United States. The population density is 1,065 per sq mi which is 2591% higher than the Oregon average and 1076% higher than the national average. The median age in Klamath Falls is 35 which is approximately 10% lower than the Oregon average of 39. In Klamath Falls, 50% of the population over 15 years of age are married, 93% speak English and 6% speak Spanish. 46% of Klamath Falls residents were born in Oregon, 48% were born out of state, 1% were born outside of the United States and 4% were foreign born.