District 21 on the 1850 Iowa Census covered all areas within present Pottawattamie, Cass, Mills, Montgomery and Adams Counties and large parts of Harrison, Shelby, Carroll, Audubon, Guthrie, Adair and Union Counties. On an 1850 Iowa census map, the original Pottawattamie County consisted of roughly 5,000,000 acres in north-western Iowa which had been formerly deeded to the Pottawattamie Indians. It was traded (for other land and money) back from them in 1846 and turned over to the state of Iowa. It included large areas south, north and east of the present day Pottawattamie county boundaries. Pottawattamie County was reorganized into five counties and parts of seven more counties beginning in 1851. There were 7828 people enumerated in District 21 in 1850. Most of these people resided in the nearly fifty+ temporary Mormon camps/towns (see-- http://winterquarters.byu.edu/pages/settlements.htm) like Council Points, Kernville (Council Bluffs) etc. that existed within the larger county in 1850. Unfortunately, there doesn't seem to be any indication on the census pages which town was being enumerated. By tracking other information on the inhabitants this can sometimes be figured out--but it is not easy. The 1850 census was the first census that listed all family members and where they were born.
The western boundary of District 21 Pottawattamie county was the Missouri river from roughly the location of the Fremont/Mills county boundary line (40.890 deg N Latitude, -95.811 deg W Long.)* to what is now the extreme eastern part of the Boyer Chute National Wildlife Refuge in Nebraska (41.55 deg N Lat. -95.919 deg W Long.)*. [Unimap (showing census districts vs. time) shows the western boundary of Pot. Co. in Iowa in 1850 to extend north along the Missouri river essentially to the Harrison/Monona county border (41.661 deg N Lat, -96.155 deg W Long.) and due east from there to Halbur and includes all of Harrison county. (see--http://www.familyhistory101.com/maps/ia_cf.html)] Dollarhide's census map shows the NE boundary from the wildlife refuge as a straight line to roughly the little town of Halbur in Carroll county (41.977 deg N Lat., -95.000 W Long.)*. The SE boundary was roughly another straight line extending SE from Halbur to roughly the center of what became the Union/Ringgold county line (40.897 deg N Lat, -94.172 deg W Long.)* The Southern boundary extended west from there along the present Iowa county boundary line(s) back to the Missouri river.
*Positions taken from 1850 Census map of Iowa shown on page 115 of "Map Guide to the U.S. Federal Censuses 1790-1920" William Thorndale and William Dollarhide, Genealogical Publishing Co. Inc. 1987. These positions are only approximate as scaled off their map; but, the boundaries were unsurveyed in 1850 so they were only approximately known then anyway.
**Unimap shows the Pottawattamie District 21 census map consists of the Missouri river from the Fremont/Mills county line north to the Harrison/Monona county line, then due east to Halbur and then a diagonal line SE to the center of the Union/Ringold county line and from there due west back to the Missouri river. [The only practical effect was whether the town of Pisgah (founded?) in Harrison county was included in the District 21 census?? (Note: this is NOT Mt. Pisgah [Thayer] in Union Co Iowa.)]