Oakland is a town in Marshall County, Oklahoma, United States. Oakland was county seat of Pickens County, Chickasaw Nation. As county seat, it hosted the county courthouse. Although never a sizable population center, the community was busy during sessions of county court, particularly since Pickens County sprawled from Chickasha in the far northwest to Mad…Oakland is a town in Marshall County, Oklahoma, United States. Oakland was county seat of Pickens County, Chickasaw Nation. As county seat, it hosted the county courthouse. Although never a sizable population center, the community was busy during sessions of county court, particularly since Pickens County sprawled from Chickasha in the far northwest to Madill in the southeast.