Lafayette, CA has a population of 25,381 and is the 1,700th largest city in the United States. The population density is 1,687 per sq mi which is 626% higher than the California average and 1762% higher than the national average. The median age in Lafayette is 45 which is approximately 24% higher than the California average of 36. In Lafayette, 66% of the population over 15 years of age are married, 86% speak English and 3% speak Spanish. 57% of Lafayette residents were born in California, 27% were born out of state, 2% were born outside of the United States and 13% were foreign born.