During their missionary journey to the Lamanites, Nephi and Lehi are thrown into the same prison "in which Ammon and his brethren were cast by the servants of Limhi." (Helaman 5:21.) Thus we find that Nephi and Lehi are doing missionary work in the land of Lehi-Nephi, because this is where Ammon and his brethren were thrown into prison by King Limhi. (See Mosiah 7:2-7.)