High Quality Content by WIKIPEDIA articles! Fort Gibson, now located in Oklahoma and designated Fort Gibson Historical Site, guarded the American frontier in Indian Territory from 1824 until 1890. When constructed, the fort lay farther west than any other military post in the United States; it formed part of the north–south chain of forts intended to maintain peace on the frontier of the American West and to protect the southwestern border of the Louisiana Purchase. The fort succeeded in its peacekeeping mission for more than 50 years, as no massacres or battles occurred there.