Consequently, you won't read about them in most Church history publications. I've documented several instances where they are referred to only as obscure letters published in the Messenger and Advocate along with lots of other long, boring articles.
So far as I've been able to discover, until my Letter VII book came out, no one published an explanation of how ubiquitous these letters were. The closest was Peter Crawley's Descriptive Bibliography of the Mormon Church.
This is strange because President Cowdery's letters deal with serious issues that people still confront today. In addition to the details about early Church history he provides, President Cowdery addressed the complaints that prophets are not perfect men (Letters II and VIII). He discussed the reasons why people do and don't accept the gospel. He explained in detail the things Moroni taught Joseph about the fulfillment of Old Testament prophecies.
Letter VII's teachings about the Hill Cumorah should have resolved that issue long ago, but that letter also deals with the question of worldly temptations when doing the Lord's work, using Joseph's hope to find something valuable to sell along with the plates.
These are just a few of the reasons why people should study these letters. When viewed this way, we can better understand why Joseph Smith made sure all the members of the Church in his day had access to the letters by publishing them in all the Church magazines.
Here's how the Joseph Smith Papers have addressed the letters. They provide a Source Note and an overall Editorial Note or Introduction.
You'll notice that in Joseph's journal entry, he refers to the letters as "President Cowdery" letters, but the Joseph Smith papers refers to them as "Oliver Cowdery's" letters. That's an editorial decision, of course, and I'm not saying it's incorrect. But it does contribute to the sense that these letters contain merely obscure opinions of Oliver's.
For Joseph Smith, though, they were President Cowdery's, reflecting Joseph's recognition that they originated with the First Presidency.
Furthermore, Joseph considered them part of "a history of my life," not merely obscure opinions.
Here is the Source Note:
The next section of the history, begun months later, is a transcript of
as his scribe, also records that Parrish “commenced writing in my journal a history of my life, concluding President Cowdery 2 letter to W. W. Phelps, which president Williams had begun.”1
Here is the link to the Editorial Note: http://www.