Rigdon remained in Ohio until February 1822, when he returned to Pittsburgh to accept the pastorate of the First Baptist Church there under the recommendation of Alexander Campbell.

Many prominent early Latter Day Saint leaders, including Parley P. Pratt, Isaac Morley, and Edward Partridge, were members of Rigdon's congregations prior to their conversion to the Church of Christ founded by Joseph Smith.

In early September 1830, Rigdon's associate, Pratt, was baptized into the Church of Christ founded by Smith.

Rigdon read the Book of Mormon in fourteen days, proclaimed its truthfulness, and was baptized into the church on November 14, 1830, in Mentor, Ohio.

[7] In December 1830, Smith said he received a revelation counseling members of the church in New York to gather to Kirtland, Ohio.

Many of the doctrines Rigdon's group had experimented with found place in the combined movement, such as living with all things in common.

Smith recorded: The next morning I went to see elder Rigdon, and found him crazy, and his head highly inflamed, for they had dragged him by his heels, and those too, so high from the earth he could not raise his head from the rough frozen surface, which lascerated it exceedingly; and when he saw me he called to his wife to bring him his razor.

On March 18, 1833,[1] Smith organized the church's First Presidency and set apart Jesse Gause and Rigdon as his first two counselors.

[1] When the church founded the Kirtland Safety Society, Rigdon became the bank's president and Smith served as its cashier.

According to one report, while the Mormons were encamped at Adam-ondi-Ahman, Rigdon criticized Smith and others who were engaged in recreational wrestling on Sunday.

Rigdon reportedly rushed into the ring, sword in hand, and said that he would not suffer a lot of men to break the Sabbath day in that manner.

Smith dragged him from the ring, bareheaded, and tore Rigdon's fine pulpit coat from the collar to the waist.

As a result of the conflict, the Mormons were expelled from the state, and Rigdon and Smith were arrested and imprisoned in Liberty Jail.

[1] Rigdon was released on a writ of habeas corpus and made his way to Illinois, where he joined the main body of Mormon refugees in 1839.

[13] Smith and his followers were allowed to escape from Liberty Jail in Missouri as ordered by Governor Boggs, and so they were released by a sheriff on their way to stand trial.

Rigdon continued to act as church spokesman and gave a speech at the ground-breaking of the Nauvoo Temple.

Charges were leveled that Rigdon had disloyal correspondences with John C. Bennett, former Governor Carlin, and "the Missourians".

In "indirect testimony" from Porter Rockwell's mother, Rigdon was accused of having had been responsible for informing others about Smith's visit to Dixon and instructing them to arrest him while there.

[16] According to the Times and Seasons, Smith had wholly removed suspicion from elder Sidney Rigdon and expressed entire willingness to have elder Sidney Rigdon retain his station, despite a lack of confidence in his integrity and steadfastness, judging from their past intercourse.

[17][18] When Smith began his campaign for the presidency of the United States in 1844, Rigdon was selected as his vice-presidential running mate.

In 1841, Rigdon had been ordained by Smith as a "Prophet, Seer, and Revelator",[14] as had all other members of the First Presidency and of the Quorum of the Twelve Apostles of the Church.

Rigdon returned to Nauvoo on August 3, and the next day he announced at a public meeting that he had received a revelation appointing him "Guardian of the Church".

The members of the quorum available in Illinois, in addition to a gathered assembly, voted to deny Rigdon his claim for church leadership.

Rigdon's branch faced less success, modernly accounting for only a small fraction of practicing Latter Day Saints.

[27][32][33] As early as 1834, skeptics were promoting what has become known as the Spalding-Rigdon theory of Book of Mormon authorship, in which Rigdon plays a central role.

According to this theory, Rigdon obtained from a Pittsburgh publisher a manuscript for a historical novel written by Solomon Spalding, and by reworking it and adding a theological component, created the Book of Mormon.

The theory that Sidney Rigdon was the true author of the Book of Mormon first appeared in print in an August 31, 1831, article by James Gordon Bennett, who had visited the Palmyra/Manchester area and interviewed several residents.

[35] This theory and the testimony of Rigdon to his son John, just prior to Rigdon's death and long after he had ceased an affiliation with any of the sects of Mormonism, contradict each other: My father, after I had finished saying what I have repeated above, looked at me a moment, raised his hand above his head and slowly said, with tears glistening in his eyes: 'My son, I can swear before high heaven that what I have told you about the origin of [the Book of Mormon] is true.

Your mother and sister, Mrs. Athalia Robinson, were present when that book was handed to me in Mentor, Ohio, and all I ever knew about the origin of [the Book of Mormon] was what Parley P. Pratt, Oliver Cowdery, Joseph Smith and the witnesses who claimed they saw the plates have told me, and in all of my intimacy with Joseph Smith he never told me but one story.'

For example, the original methodology, when replicated, also assigns Rigdon as the probable author of The Federalist Papers, which were written five years before his birth.