Oakmont Country Club is a country club in the eastern United States, located mostly in Plum with only a very small portion of the property located in Oakmont, suburbs of Pittsburgh in western Pennsylvania. Established 121 years ago in 1903, its golf course is regarded as the "oldest top-ranked golf course in the United States." It was designate…Oakmont Country Club is a country club in the eastern United States, located mostly in Plum with only a very small portion of the property located in Oakmont, suburbs of Pittsburgh in western Pennsylvania. Established 121 years ago in 1903, its golf course is regarded as the "oldest top-ranked golf course in the United States." It was designated a National Historic Landmark in 1987. The Pennsylvania Turnpike separates seven holes from the rest of the course.