Helaman 1 - 4

During the period that Helaman, son of Helaman, sat on the judgement-seat -

"...there were an exceedingly great many who departed out of the land of Zarahemla, and went forth unto the land northward to inherit the land.
4 And they did travel to an exceedingly great distance, insomuch that they came to large bodies of water and many rivers..." (Book of Mormon Helaman 3:3 - 4)

"And there being but little timber upon the face of the land, nevertheless the people who went forth became exceedingly expert in the working of cement; therefore they did build houses of cement, in the which they did dwell." (Book of Mormon Helaman 3:7)

And -

"...as timber was exceedingly scarce in the land northward, they did send forth much by the way of shipping.
11 And thus they did enable the people in the land northward that they might build many cities, both of wood and of cement." (Book of Mormon Helaman 3:10 - 11)

Mormon also tells us -

"...now there are many records kept of the proceedings of this people, by many of this people, which are particular and very large, concerning them.
14 But behold, a hundredth part of the proceedings of this people, yea, the account of the Lamanites and of the Nephites, and their wars, and contentions, and dissensions, and their preaching, and their prophecies, and their shipping and their building of ships, and their building of temples, and of synagogues and their sanctuaries, and their righteousness, and their wickedness, and their murders, and their robbings, and their plundering, and all manner of abominations and whoredoms, cannot be contained in this work.
15 But behold, there are many books and many records of every kind, and they have been kept chiefly by the Nephites." (Book of Mormon Helaman 3:13 - 15)

And also during this period -

"...there was exceedingly great prosperity in the church, insomuch that there were thousands who did join themselves unto the church and were baptized unto repentance.
25 And so great was the prosperity of the church, and so many the blessings which were poured out upon the people, that even the high priests and the teachers were themselves astonished beyond measure.
26 And it came to pass that the work of the Lord did prosper unto the baptizing and uniting to the church of God, many souls, yea, even tens of thousands.
27 Thus we may see that the Lord is merciful unto all who will, in the sincerity of their hearts, call upon his holy name." (Book of Mormon Helaman 3:24 - 27)

And this great prosperity and happines in the church was because of the words of Christ that was made available and preached to the people for -

"..we see that whosoever will may lay hold upon the word of God, which is quick and powerful, which shall divide asunder all the cunning and the snares and the wiles of the devil, and lead the man of Christ in a strait and narrow course across that everlasting gulf of misery which is prepared to engulf the wicked—
30 And land their souls, yea, their immortal souls, at the right hand of God in the kingdom of heaven, to sit down with Abraham, and Isaac, and with Jacob, and with all our holy fathers, to go no more out." (Book of Mormon Helaman 3:29 - 30)