Located in southwestern Washita County, Sentinel lies at the intersection of State Highways 44 and 55.

In 1898, R. B. Gore, a pioneer of Old Greer County, established a small general merchandise store in the area and applied for a post office.

On March 6, 1899, the Post Office Department approved the application and designated the locale as Sentinel, Oklahoma Territory.

The newly formed Orient Townsite Company chose the site of present Sentinel and received a donation of eighty acres from L. N. Whitmer.

The new residents asked Gore to relocate his store and post office to the new location.

Determined to correct the name problem, he started a petition to incorporate the town as Sentinel.

In 1911 residents supported two banks, a newspaper, electricity and telephone service, four grocers, two hotels, four general stores, among many other businesses and professionals.

In 1961, the chamber of commerce began hosting an annual, large July Fourth celebration.

[5] According to the United States Census Bureau, the town has a total area of 0.6 square miles (1.6 km2), all land.

The Sentinel School District has a large geographic area consisting of over 200 square miles (520 km2).