- Marion is a city in Grant County, Indiana, United States. It is the county seat of Grant County and had a population of approximately 29,700 as of the 2020 census. Marion is located in the northeastern part of Indiana and is about 68 miles northeast of the state capital, Indianapolis. The city is known for its manufacturing history and is home to several factories and industrial facilities. Marion offers a variety of amenities and attractions, including parks, sports facilities, museums, and local events.