The Sedan shot resulted in a radioactive cloud that separated into two plumes, rising to 3.0 km and 4.9 km (10,000 ft and 16,000 ft). The two plumes headed northeast and then east in roughly parallel paths towards the Atlantic Ocean. Nuclear fallout was dropped along the way, narrowly dispersed in a relatively small number of United States counties. Detected radioactivity was especially high in eight counties in Iowa and one county each in Nebraska, South Dakota and Illinois. The most heavily affected counties were Howard, Mitchell and Worth counties in Iowa as well as Washabaugh County in South Dakota, an area that has since been incorporated into Jackson County and is wholly within the Pine Ridge Indian Reservation. These four counties measured maximum levels higher than 6,000 microcuries per square meter (220 MBq/m2).