I view the Southwest Iowa counties as arranged in horizontal tiers. Tier 1 is along the Missouri border. Tier numbers increase as one moves northward.
- A very large Pottawattamie County was established in 1847, along with the four Southwest Iowa tier 1 counties, using land formerly in the Potawatomi Reserve.
- The remaining 14 Southwest Iowa counties were established in 1851, most using all or a portion of the 1847 Pottawattamie County.
Land was surveyed into 160-acre parcels. In Southwest Iowa, surveying began in the early 1850s and was complete by 1855.
The private sector then acquired the land through a government land office. Acquisition could be by one of several modes:
- Purchase for $1.25 per acre in a land office or for $1.25 or more at a land office auction.
- Exchange for a warrant previously issued to a veteran, often a Mexican War veteran.
- Land grants to selected railroads.