Greenbrier is a city in Faulkner County, Arkansas, United States. It is part of the Central Arkansas region. The population was 5,707 at the 202…Greenbrier is a city in Faulkner County, Arkansas, United States. It is part of the Central Arkansas region. The population was 5,707 at the 2020 census, up from 4,706 at the 2010 census. Prior to European settlement, Native American tribes, including the Quapaw and later the Cherokee, lived in the area. Several historical figures of the Wild West such as Jim Bowie and Jesse James passed through the Greenbrier region toward Oklahoma and Texas. The Wiley brothers settled near East Fork Cadron around 1818, about 8 miles east of today's Greenbrier. In 1837, Jonathan Hardin settled near the Wiley settlement. Also in the early 19th century, the Casharagos settled north of Greenbrier in the present community of Republican.