Rachel (Harris) Oakes Preston (2 March 1809-1 February 1868) was a Seventh Day Baptist who persuaded a group of Adventist Millerites to accept Saturday, instead of Sunday, as the Sabbath.
This Sabbatarian group organized as the Seventh-day Adventist Church in 1863.
Born in Vernon, Vermont, Rachel, daughter of Sylvanus Harris, first joined the Methodist Church.
After marrying Amory Oakes, Rachel moved to Verona, New York, where her husband soon died.
In 1837 Rachel and her daughter, Rachel Delight Oakes, joined the Seventh Day Baptist Church of Verona.
In 1843 the widowed Rachel and her daughter moved to Washington, New Hampshire, where her daughter would teach school.
While attending the "Christian Brethren" church with her daughter, Rachel tried to present her views on the seventh-day Sabbath.
Due to Rachel's influence, Frederick Wheeler (1811-1910), an ordained minister of the Methodist Episcopal Church, and promoter of the prophetic teachings of William Miller, preached his first sermon on the seventh-day Sabbath to his "Christian Brethren" congregation on 16 March 1844.
Further due to Rachel's influence, William Farnsworth (1807-1888), stated publicly to the "Christian Brethren" congregation his conviction that Saturday, being the seventh day of the week, was the Sabbath.
His brother Cyrus (who became the husband of Rachel’s daughter Delight), and several others, also made their convictions known.
Later, when Rachel married Nathan T. Preston, she was referred to as Rachel Oakes Preston.