The Eastland Oil Company is a privately held exploration and production company. Started in New York by A.M. Donnelly, it was originally the A.M. Donnelly Drilling Company. Moving to Oklahoma in 1905, the drilling company drilled in and around Coffeyville, Kansas, along with the towns of Nowata and Okmulgee, Oklahoma. The first wells in Texas were drilled in Denton County in 1914. Also in 1914, they were contracted by Mid-West Oil to drill in the Artesia Field in New Mexico. The company then started drilling in Eastland County, Texas in 1918. Finding the Martin Field in Eastland County in 1921, the company incorporated The Eastland Oil Company in 1922. The company's headquarters were in Fort Worth, Texas from 1924 until 1977 when it was moved to Midland, Texas.
The company is now managed by the 4th generation of the family, with its employees having over 100 years of combined experience in the oil and gas fields of the Permian Basin.