Stephenville, TX has a population of 19,561 and is the 2,225th largest city in the United States. The population density is 1,646 per sq mi which is 1598% higher than the Texas average and 1716% higher than the national average. The median age in Stephenville is 25 which is approximately 28% lower than the Texas average of 34. In Stephenville, 42% of the population over 15 years of age are married, 86% speak English and 13% speak Spanish. 71% of Stephenville residents were born in Texas, 24% were born out of state, 1% were born outside of the United States and 4% were foreign born.