Gas City is a city in Grant County, Indiana, along the Mississinewa River. The population was 5,965 at the 2010 census. It was first known as Harrisburg when settled on May 25, 1867 by Noah Harris. It became something of a boom town when natural gas was found in the area in 1887. The Gas City Land Company was founded on March 21, 1892 and the town of about 150 people changed its name to Gas City a few days later.