Southlake, TX has a population of 29,101 and is the 1,469th largest city in the United States. The population density is 1,333 per sq mi which is 1275% higher than the Texas average and 1371% higher than the national average. The median age in Southlake is 42 which is approximately 23% higher than the Texas average of 34. In Southlake, 73% of the population over 15 years of age are married, 89% speak English and 4% speak Spanish. 39% of Southlake residents were born in Texas, 50% were born out of state, 2% were born outside of the United States and 10% were foreign born.