Oliver H. P. Cowdery[2] (October 3, 1806 – March 3, 1850) was an American religious leader who, with Joseph Smith, was an important participant in the formative period of the Latter Day Saint movement between 1829 and 1836.

Cowdery met Joseph Smith, Jr. on April 5, 1829—a year and a day before the official founding of the Church of Christ—and heard from him how he had received golden plates containing ancient reformed Egyptian writings.

Working with Cowdery, however, Smith completed the manuscript of what would become the Book of Mormon between April 7 and June 1829, in what Richard Bushman later called a "burst of rapid-fire translation.

[16][17] Cowdery helped Smith publish a series of revelations first called the Book of Commandments and later, as revised and expanded, the Doctrine and Covenants.

He was also the editor, or on the editorial board, of several early church publications, including the Evening and Morning Star, the Messenger and Advocate and the Northern Times.

Cowdery felt that Smith's integration of economic and political plans into religious matters was encroaching on the separation of church and state.

A dirty, nasty, filthy affair of his and Fanny Alger's was talked over in which I strictly declared that I had never deserted from the truth in the matter, and as I supposed was admitted by himself.

"[19]: 323–325, 347–349 In January 1838, Smith and Rigdon left Kirtland and took over the Far West, Missouri church in March 1838, which had previously been under the presidency of W. W. Phelps and David Whitmer—a close friend and brother-in-law to Cowdery.

[20] Nine excommunication charges were presented against Cowdery, which included selling lands in Jackson County without authorization, trying to destroy the character of Joseph Smith, and disregarding his ecclesiastical duties for the practice of law.

[23] Cowdery refused to appear before the council, but sent a letter of resignation, reiterating his desire to live his religious beliefs independent from his economic and political decisions.

These men were became collectively known as "dissenters", but continued to live in and around Far West, where they owned a great deal of property, much of which was purchased when they were acting as agents for the church.

Reports about their treatment circulated in nearby non-Mormon communities and increased the tension that led to the 1838 Mormon War, which ultimately resulted in the Latter-Day Saints' expulsion from Missouri.

[28] In 1848, Cowdery traveled to the frontier settlement of Winter Quarters (in present-day Nebraska) to meet with followers of Brigham Young and the Quorum of the Twelve, asking to be reunited with the church.

[31] On November 12, 1848, Cowdery was rebaptized by Orson Hyde of the Quorum of the Twelve into—what had become following the succession crisis—the LDS Church in Indian Creek at Kanesville, Iowa.

After his rebaptism, Cowdery desired to relocate to the State of Deseret (present-day Utah) in the coming spring or summer, but due to financial and health problems he decided that he would not be able to make the journey in 1849.

However, in July 1849, Young wrote Cowdery a letter inviting him to travel to Washington, D.C., with Almon W. Babbitt to press the State of Deseret's desire for statehood and to draft a formal application.

LDS scholar Daniel Peterson argues against this theory noting that analysis of the manuscripts indicates that the Book of Mormon was primarily the product of Joseph Smith's dictation, rather than a collaborative effort — it contains aural errors, typical of a transcription process.

Additionally, the Printer's Manuscript, which Cowdery assisted in producing, contains significant copyist errors in his handwriting, suggesting he was not fully aware of the book's content beforehand.

[citation needed] Joseph Smith, Sr. and Cowdery's father, William, may have been members of a Congregationalist sect known as the New Israelites, organized in Rutland County, Vermont.

[42][43] In 2000, David Persuitte argued that Cowdery's knowledge of View of the Hebrews significantly contributed to the final version of the Book of Mormon,[44] a connection first suggested as early as 1902.