In Alma 14:7 we learned that some believers in Ammonihah had been cast out, apparently forced out by casting stones at them to encourage them to leave. They went to Sidom, and Alma and Amulek went to Sidom. This suggests that Sidom was friendly to both the Nephite government and religion, and that it was the most logical way to travel to another city. It was probably reasonably close, and may have been connected by known paths, if not actual roads.
The immigrants to Sidom meet with Alma and Amulek and exchange stories.