Winfield, KS has a population of 12,283 and is the 3,351st largest city in the United States. The population density is 1,102 per sq mi which is 3042% higher than the Kansas average and 1116% higher than the national average. The median age in Winfield is 36 which is approximately 1% lower than the Kansas average of 36. In Winfield, 53% of the population over 15 years of age are married, 92% speak English and 4% speak Spanish. 66% of Winfield residents were born in Kansas, 30% were born out of state, 0% were born outside of the United States and 4% were foreign born.