Joseph's manuscript history identifies the town in Iowa to be built to be called Zarahemla.

Date: Jul 2, 1839
Type: Manuscript
Source: Joseph Smith, Jr.
LDS
Hearsay: Direct
Reference: Joseph Smith, History Draft [6 August 1838–30 December 1839], 61, Joseph Smith Papers
Scribe/Publisher: Willard Richards
People: Hyrum Smith, Sidney Rigdon, Newel K. Whitney, Vinson Knight, Joseph Smith, Jr.
Audience: N/A
Transcription: <visit to Iowa.> <2> Tuesday 2 spent the forenoon of this day on the Iowa side of the River. Went in Co with Elders [Sidney] Rigdon, H[yrum] Smith, & Bishops Whitny [Newel K. Whitney] & [Vinson] Knight, & others to visit a pu[r]chase lately made by the church Bishop Knight as a location for a town, and advised that a town be built there <and be called Zarahemla>.
Source Link: https://www.josephsmithpapers.org/paper-summary/history-draft-6-august-1838-30-december-1839/63