Eliza Northrup McMillan was born on June 23, 1845 in Aylmer, Ontario, Canada. The daughter of daughter of George and Mary (McConnell) Northrup, Eliza married William McMillan in 1863. In 1867, the McMillans left Canada for Detroit, Michigan where William opened the wholesale hardware store of William McMillan and Co.

In April 1870, they moved to St. Louis, Missouri where William established the Missouri Car and Foundry Co. This later merged with the American Car and Foundry Co. The McMillans resided at 25 Portland Place in a home designed by Eames and Young.

The McMillan's had three children, Mary, Percy, and William Northrup.  William Northrup McMillan was born in 1872. He became a hunter and explorer who lived his later years in Nairobi, Kenya. While in Africa, he became a British citizen and awarded the honor of Knighthood for his services to the British Empire and to East Africa.

The McMillans gave $100,000 to Mary Institute, a college preparatory school formerly run by Washington University, to move out of its old, rundown building and into a new building. After her husband’s death in 1901, Eliza continued to give generously to the poor and unfortunate. In addition to various smaller donations to programs, such as the Washington University Art Department Fund, she gave $300,000 to establish McMillan Hall for women students as memorial to her husband. McMillan Hall was the first visible and substantial acknowledgement by the university of women's presence on the new campus. Eliza became an honorary member of the Woman’s Club of Washington University in 1911. She also purchased the Phillips School, presented it to the St. Louis Academy of Science, and donated $100,000 to Mary Institute for new buildings.

In December 1914, Eliza traveled to Pasadena, California with the hope of improving her declining health where she died on January 16, 1915. She is buried in Bellefontaine Cemetery. When she died, among those included in her will were friends and family, as well as her household staff, to whom she gave “lifetime” salaries. She also bequeathed Washington University funds for an eye, ear, nose, and throat hospital for the medical school, also to be named for her husband. In 1925, the funds from the bequest became available and by 1929, the gift was valued at $1,200,000. For a number of years it was the tallest building in the growing medical school complex.

Note written by Sarah Schnuriger