Otisco is an unincorporated community in Charlestown Township, Clark County, Indiana.Otisco was laid out in 1854 when the railroad was extended to that point. According to one source, the name might be borrowed from New York's Otisco Lake.The Otisco post office was established in 1870.Otisco is located at 38°32′32″N 85°40′02″W / 38.54222°N 85.66722°W / 38.54222; -85.66722 along Indiana State Road 3 in the northern corner of Charlestown Township. The northern fringe of the town extends into neighboring Oregon Township.