Four times the word "up" is used to refer to the Nephites going against the Lamanites to battle (Mormon 3:10, 14, 16; 4:1). Assuming a Mesoamerican setting, the Nephite "narrow pass" might be located somewhere along the narrow travel corridor through the Isthmus of Tehuantepec, which is mostly a lowland route from the Pacific coast on the south ("west") to the Gulf of Mexico coast on the north ("east"). If the Nephites were going "up" they might have been going into that wilderness (mountain) strip which was described in Alma 22:29 as going "round about on the wilderness side on the north [of Zarahemla] even until they [the Nephites at that time] came to the land which they called Bountiful." Putting this in a Mesoamerican setting, the Nephites would have been going up into a range of mountains which sweeps from the Pacific Coast towards the Gulf of Mexico and borders the coastal corridor through the Isthmus of Tehuantepec. [Alan C. Miner, Personal Notes]
Geographical [Theory Map]: Mormon 3:9--4:1 The Nephites Wage War (363 A.S.)