Medford is a city in and the county seat of Grant County, Oklahoma, United States. As of the 2010 census, the city population was 996. T…Medford is a city in and the county seat of Grant County, Oklahoma, United States. As of the 2010 census, the city population was 996. The Encyclopedia of Oklahoma History and Culture states only that the town name was for Medford, Massachusetts, which it says was the home town of a railroad official.