The author labored to give his words and phrases the quaint, old-fashioned sound and structure of our King James's translation of the Scriptures.... Whenever he found his speech growing too modern -- which was about every sentence or two -- he ladled in a few such Scriptural phrases as "exceeding sore," "and it came to pass," etc., and made things satisfactory again. "And it came to pass" was his pet. If he had left that out, his Bible would have been only a pamphlet. Roughing It, Chapter 16

Anyone who reads the Book of Mormon (BoM) will notice that the phrase "and it came to pass" is used way too often. Mark Twain had this to say about it:

The phrase is also, of course, frequently found in the King James Version of the Bible, which is no doubt why Joseph Smith used it in the BoM; it just sounds so darned biblical. The trouble is that he liked it so much that he got carried away with it. Here's a summary of the occurrences of "it came to pass" in the Bible and the BoM.

Bible BoM it came to pass 452 1424

The phrase occurs more than three times as often in the BoM as in the Bible. That doesn't seem so bad until you look at the size of the two books. The Bible is nearly five times as big as the BoM. Here's how the comparison looks when size is taken into account.

Bible BoM it came to pass 452 1424 number of verses 31,102 6553 Occurrences per 100 verses 1.45 21.7

So "it came to pass" is found in more than 20% of the BoM's verses -- 15 times as often as in the Bible! But, actually, it's a bit worse than that. The original 1830 edition of the BoM had even more uses of "and it came to pass." But since I can't find a searchable version of the 1830 edition, I can't quantify it for you.

Of course all of this can be explained. Brant A. Gardner in Meridian Magazine tells us that there's a good reason for all the and-it-came-to-passes; Joseph Smith used this phrase to mark the beginning of paragraphs. It's just that simple.

Still it seems strange that he would have had 30 paragraphs in the 39 verses of 1 Nephi 16. I guess the original translation didn't have any punctuation, but still 30 paragraphs in 45 or so sentences seems a bit excessive.

And if the and-it-came-to-passes were used to mark new paragraphs, why do some verses have more than one. Here's Alma 47:11, for example:

And it came to pass that when Lehonti received the message he durst not go down to the foot of the mount. And it came to pass that Amalickiah sent again the second time, desiring him to come down. And it came to pass that Lehonti would not; and he sent again the third time.

Did Joseph Smith really think there should be three paragraphs in this verse?

No, it looks to me like Mark Twain had it exactly right. Joseph Smith thought the and-it-came-to-passes made it sound like scripture, and it would make his rather short book a bit longer. So he couldn't resist.