New Castle is a city in Henry County, Indiana, 44 miles east-northeast of Indianapolis, on the Big Blue River. In 1900 , 3,406 people lived in the town; in 1910 , 9,446; in, 1920 14,458; and in 1940, 16,620. The population was 17,780 at the 2000 census. The city is the County seat of Henry County. New Castle is home to New Castle Field House, the largest high school gymnasium in the world. The city is surrounded by a farming district. In the past, it was an industrial center of some importance, where the leading manufactures included sheet iron and steel, automobiles, caskets, clothing, scales, bridges, pianos, furniture, handles, shovels, lathes, bricks, flour, etc.