DECATUR, a city of eastern Indiana, U.S.A., on St. Mary's river, loom. N.E. of Indianapolis; the county seat of Adams county. It is on Federal highway 27, and is served by the Erie, the Nickel Plate and the Pennsylvania railways. The population was 4,762 in 1920 (97% native white) and was 5,156 in 1930 by the Federal census. It is surrounded by a farming and lumbering region, and has various factories. Decatur was settled about 1836 and incorporated in 1882.