|Mormon 1:3 indicates that the land Antum was near the land where Mormon was born, as you don't have to go over to that land, up to it, or down to it. Since I believe Mormon was born and raised in Teotihuacan, I believe the land Antum was close to that city. The record keeper Ammaron was living in the same city as Mormon, as he was tutoring the young Mormon, and it was Ammaron who had hid the records in the hill Shim, (see Mormon 1:3). I assume therefore that the land Antum was close to where Ammaron and Mormon were living. I believe this to be the valleys of Puebla and Tlaxcala, in Central Mexico. In the valley of those two states is a hill named The Malenchi, which I believe to be the hill Shim.
This land is called the land Antum, not the land of Antum, which means the name was descriptive, and not named after a person.
I Nephi 17:5 indicates that the place where all the waters end up, (the ocean), was called Irreantum by the Nephites. I have extrapolated from this, that the name Antum is where all the waters begin to run, the continental divide. The states of Puebla and Tlaxcala are at the very continental divide of Mexico, which I believe to be the land Antum, where the waters begin to flow. One of the major cities in the state of Puebla is that of Cholula, whose name means, "Where the waters begin to flow."