It is easy to see these verses in the context of the people who went north, and perhaps more specifically with the people of Ammon. That is not the case. When Mormon mentions “this people” in verse 14, he is referring to the Nephites. This becomes clear when he notes that the records are “the account of the Lamanites and of the Nephites.” Mormon is speaking of the large plates that are kept by the Nephites. There are many, and he can only write the hundredth part of what is on them.
The identification of this record with the large plates is confirmed in verse 16 when Mormon indicates that they have been handed down among the Nephites, until the Nephites became wicked and were destroyed; that is, until Mormon’s time.