Where was the land of Desolation? This is a little tricky. Let me tell you why.
The first mention of the land of Desolation is in Alma 22:30. Verse 29 gives some context to its location. “The Nephites had taken possession of all the northern parts of the land bordering on the wilderness, at the head of the river Sidon, from the east to the west round about on the wilderness side; on the north, even until they came to the land which they called Bountiful.” Here’s what I read. The head of the river Sidon is the sum of, not the beginning. So the river Sidon runs into a sea. An inland sea or not, we don’t know. It would make sense if it were. It would explain why the Lamanites had to go north to get to Zarahemla, which was south. They had to go “round about” this inland sea.
There was a wilderness that bordered this sea and then they went north to the land called Bountiful. (Interesting that the land Bountiful is the only land not described as the land of Bountiful.) “An it bordered upon the land which they called Desolation, it being so far northward that it came into the land which had been peopled and been destroyed of whose bones we have spoken, which was discovered by the people of Zarahemla, it being the place of their first landing.” It’s important that we understand who are they talking about when they say their. The way it’s worded it could be the people of Zarahemla. But when you look at the footnote to the word “first” (d) it tells you who Their is. Ether 6:12 “And they (the Jaredites) did land upon the shore of the promised land. And when they had set their feet upon the shores of the promised land they bowed themselves down upon the face of the land…” We didn’t know this distinction until the current revised and expanded scriptures were printed in 1979.
So the people of Zarahemla did not land north of the land of Desolation. They landed south and stayed where Moshiah found them. And we know this because in Omni 16 “And they (the people of Zarahemla) journeyed in the wilderness, and were brought by the hand of the Lord across the great waters, into the land where Moshiah discovered them; and they had dwelt there from that time forth.” That is saying to me that the people of Zarahemla landed and stayed where Moshiah discovered them. That would explain why the Nephites never knew of the people of Zarahemla for more than 300 years. The Nephites stayed when he left Laman and Lemuel. And we know that Zarahemla was north of where Lehi landed because of Hel 6:10, “Now the land south was called Lehi, and the land north was called Mulek, which was after the son of Zedekiah; for the Lord did bring Mulek into the land north, and Lehi into the land south.” Meaning the land southward was Lehi and the land northward was Mulek. Not north as above the land of Desolation.
Sometimes we might think the land of Desolation is where the Jaredites lived, but I don’t necessarily think so. Listen to Moroni’s description of the land of Moron in Ether 7:6. “Now the land of Moron, where the king dwelt, was near the land which is called Desolation by the Nephites.” This is during the time of the Jaredites. I don’t read anything that for certain tells us the land of Desolation is where the Jaredites lived. On the other hand, why are they calling it the land of Desolation?
Another curious description of the land of Desolation is in Alma 63:5. “And it came to pass that Hagoth, he being a exceedingly curious man, therefore he went forth and built him an exceedingly large ship, on the borders of the land Bountiful and by the land Desolation, and launched it forth into the west sea, by the narrow neck which led into the land northward.” If the west sea is on the Pacific Ocean, this description could work. If the west sea is the inland sea, this could also work. And then we read this, “And they built a great city by the narrow neck of land by the place where the sea divides the land.” (Ether 10:20) A narrow neck of land but also the place where the sea divides the land. An inland sea can have an outlet to an ocean, for example the Mediterranean Sea. Its outlet is through the straits of Gibraltar. There is a 9-mile opening where the sea divides that land.