New Castle is a city in Henry County, Indiana, 44 miles (71 km) east-northeast of Indianapolis, on the Big Blue River. The city is the county seat of Henry County. New Castle is home to New Castle Fieldhouse, the largest high school gymnasium in the world. The city is surrounded by agricultural land. In the past, it was a manufacturing center for the production of sheet iron and steel, automobiles, caskets, clothing, scales, bridges, pianos, furniture, handles, shovels, lathes, bricks, and flour. Starting in the early 20th century, it was known as the Rose City, at one point having 100 florists and numerous growers.
According to the 2010 census, the population was 18,114.
New Castle Correctional Facility, with a capacity of over 3,500 inmates, is located just north of the city.
New Castle was platted in 1823, and named after New Castle, Kentucky. A post office was established at New Castle in 1823. The Maxwell automobile factory, later owned and operated by Chrysler Motor Corp.