Greenbrier, AR has a population of 5,164 and is the 6,315th largest city in the United States. The population density is 650 per sq mi which is 1073% higher than the Arkansas average and 618% higher than the national average. The median age in Greenbrier is 29 which is approximately 24% lower than the Arkansas average of 38. In Greenbrier, 69% of the population over 15 years of age are married, 97% speak English and 2% speak Spanish. 65% of Greenbrier residents were born in Arkansas, 33% were born out of state, 1% were born outside of the United States and 1% were foreign born.