Mary was born in Cambuslang, Lanark(shire), Scotland, daughter of James McGowan and Mary Pollock McGowan. She married Charles Stewart Miller in 1824.
Mary, her husband Charles Stewart Miller, and their family joined the LDS (Mormon) Church in 1846 in Rutherglen, Lanark(shire), Scotland. They sailed to America in 1848 with their 11 children on the "Carnatic" (as soon as emigration to "Zion" was re-instated following Joseph Smith's martyrdom, the "Carnatic" was the first ship of LDS converts from Scotland to sail). This was before the Perpetual Emigration Fund, so they had to pay their way up front. After landing in America, most LDS emigrants of the time found work in the east or midwest for a year or more, in order to fund the remainder of their journey. The Millers found work in Gravois just outside of St. Louis, Missouri, in the "coal diggings".

Tragically, Mary, 46, her husband Charles, 44, and their sons William, 17, and Archibald, 15, died in a cholera epidemic in the summer of 1849, within 10 days of each other.

An extract from a talk entitled "Constant Truths for Changing Times" by LDS President Thomas S. Monson:

"I admonish all families: search out your heritage. It is important to know, as far as possible, those who came before us. We discover something about ourselves when we learn about our ancestors.

"I recall as a boy hearing of the experiences of my Miller ancestors. In the spring of 1848, my great-great-grandparents, Charles Stewart Miller and Mary McGowan Miller, joined the Church in their native Scotland, left their home in Rutherglen, Scotland, and journeyed across the Atlantic Ocean. They reached the port of New Orleans and traveled up the Mississippi River to St. Louis, Missouri, with a group of Saints, arriving there in 1849. One of their 11 children, Margaret, would become my great-grandmother.

"When the family arrived in St. Louis, planning to earn enough money to make their way to the Salt Lake Valley, a plague of cholera struck the area. The Miller family was hard-hit: in the space of two weeks, mother, father, and two of their sons died. My great-grandmother, Margaret Miller, was 13 years old at the time.

"Because of all the deaths in the area, there were no caskets available--at any price. The older surviving boys dismantled the family's oxen pens in order to make crude caskets for the family members who had passed away.

"The nine remaining orphaned Miller children and the husband of one of the older daughters left St. Louis in the spring of 1850 with four oxen and one wagon, arriving finally in the Salt Lake Valley that same year.

"I owe such a debt of gratitude to these and other noble forebears who loved the gospel and who loved the Lord so deeply that they were willing to sacrifice all they had, including their own lives, for The Church of Jesus Christ of Latter-day Saints. How grateful I am for the temple ordinances which bind us together for all eternity."