Derby, KS has a population of 23,847 and is the 1,835th largest city in the United States. The population density is 2,327 per sq mi which is 6534% higher than the Kansas average and 2469% higher than the national average. The median age in Derby is 35 which is approximately 2% lower than the Kansas average of 36. In Derby, 65% of the population over 15 years of age are married, 97% speak English and 1% speak Spanish. 56% of Derby residents were born in Kansas, 40% were born out of state, 2% were born outside of the United States and 3% were foreign born.