And we did observe to keep the judgements, the statutes, and the commandments of the Lord in all things, according to the law of Moses. (2 Ne. 5:10)
Nephi and his brothers returned to Jerusalem to get the brass plates which contained the law of Moses. It is clear in the Book of Mormon that the people of Nephi lived the law of Moses. They used the brass plates to establish civil law and keep the religious festivals.
The law of Moses relies heavily on the availability of lambs and goats for ritual sacrifice. In order to live the law properly, the promised land had to have an environment where these animals could thrive. It is interesting to note, that sheep and goats are indigenous to North America.
In fact, in the book Archeology of New York State, W.A. Ritchie claims proof of domesticated sheep in New York dating back to 100 AD. These are exciting times for members of the Church of Jesus Christ of latter-day Saints. Not only do we have the spirit to testify of truth, we often have scientific studies that support truth as well.
It is most important to seek a spiritual witness of the Book of Mormon. This vital witness can be obtained by following the directions in Moroni 10 of the Book of Mormon.
To hear more interesting factual information, I recommend the following presentation by Amberli Nelson.