The gold plates that were delivered to Joseph Smith amounted to about a "hundredth part" of the total recorded history if the references in the record itself are correct (Jacob 3:13, Helaman 3:14, Ether 15:13). In other words, we might say that the entire collection of plates that Ammaron turned over to Mormon occupied 100 times the volume and weighed 100 times the weight as the set of plates eventually given to Joseph Smith. If that truly was the case, then considering the circumstances, how far or to what distance would Ammaron travel from where he lived in order to "hide up these records"? One should notice here that there is no mention or any attempt to indicate any long journey or extended travel in order to reach the site where these records were hidden (the hill Shim).
Mormon was only 10 years old when he was entrusted with these records (Mormon 1:2). Mormon would be taken southward to the land of Zarahemla when he was age 11 (Mormon 1:6). This means that sometime between his calling at age 10 and his obtaining the records at age 24 (Mormon 1:3), Mormon would have had to gain some very distinct geographical knowledge of the land Antum and the hill Shim. All these records had been cared for by men who up until this time were all located in the Land Southward (Nephi, Zarahemla, and Bountiful). It doesn't seem very practical at all for Ammaron to be in charge of recording the history of a people thousands of miles away from where he himself was living. Thus, if Ammaron hid the plates in the Hill Shim in the Land Antum (Mormon 1:3). And if the Hill Shim was mentioned in the same scripture with the location of the Hill Cumorah (Ether 9:3) Then both the Hill Shim and the Hill Cumorah might have been located not only somewhat near to each other, but within a few hundred miles of the land of Zarahemla. [See also the commentary on Mormon 1:3; 3:5]
4 Nephi 1:48 All the sacred records which had been handed down from generation to generation ([Illustration]): Sources, plates, records, and manuscripts of the Book of Mormon. [John W. Welch ed., Reexploring the Book of Mormon, p. 17]
Note* For a more complete listing, the reader is referred to Appendix B
Geographical [Theory Map]: 4 Nephi 1:48-49 Ammaron Hides up the Plates -- Chooses Mormon (321 A.S.)