Helaman 6:7-8 reports at about the time of Christ, "the Nephites did go into whatsoever part of the land they would, whether among the Nephites or the Lamanites. And . . . the Lamanites did also go whithersoever they would. . .; and thus they did have free intercourse one with another, to buy and to sell, and to get gain." (3 Nephi 6:8,12 imply the same thing).
John Sorenson notes that at a few points in the Book of Mormon account we read of extensive commerce. It is impossible that a civilization that included widespread trade and related components--record keeping, craft production, knowledge of routes, and so on--would have arisen suddenly at just those moments. The pattern must have been going on for a long time, becoming particularly visible when it reached a climax level. [John L. Sorenson, Mormon's Map, F.A.R.M.S., pp. 101-102]