Susanville, CA has a population of 15,555 and is the 2,750th largest city in the United States. The population density is 1,958 per sq mi which is 743% higher than the California average and 2061% higher than the national average. The median age in Susanville is 32 which is approximately 10% lower than the California average of 36. In Susanville, 36% of the population over 15 years of age are married, 75% speak English and 20% speak Spanish. 75% of Susanville residents were born in California, 18% were born out of state, 1% were born outside of the United States and 6% were foreign born.