Hartford City is a city in the U.S. state of Indiana, and the county seat of Blackford County. Located in the northeast central portion of the state, the small farming community underwent a dramatic 15-year economic boom beginning in the late 1880s. The Indiana Gas Boom resulted from the discovery and exploitation of natural gas in the area. The rural economy was transformed to one that included manufacturing. The boom attracted workers and residents, retail establishments, and craftspeople.