Margaret McIlvaine (maiden name unknown) was born on March 20, 1840, in Manhasset, New York. She married Henry B. McIlvaine on November 20, 1860, and they had at least four children, including: Catherine, born around 1865; Helen, born around 1869; and Harriet, born around 1860. Their first child, born in the early 1860s, may have died in 1864. Her husband served in the Union army from November 1861 until December 1864.
They lived in North Hempstead, New York, and her husband worked as a farmer. By 1870, they owned $50,000 of real estate and $8,000 of personal property, and they employed at least three white domestic servants. They moved to Faribault, Minnesota, around 1876. Her husband died there on June 15, 1883. She remained in Faribault, and her daughter Catherine lived with her for the rest of her life. She died there on August 24, 1920.