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 experienced a 15-year economic boom beginning in the late 1880s - the Indiana Gas Boom, caused by the discovery of natural gas in the area, which transformed the area from an agricultural economy to one that also included manufacturing. The boom brought residents, retail establishments, and craftspeople. The increased population meant construction of roads, schools, and churches. After the boom came a long period of growth and stability. Agriculture (and agricultural trade) remained as the fundamental industry.