Alexander McKay was an early miner and pioneer in the Alder Gulch, Montana, area. He was born on May 15, 1832, in Glasgow, Scotland, and immigrated to the United States in 1854. The McKays spent their first years in this country in the South. In the late 1850s they moved to the Denver area following mining opportunities. They then moved to Bannack, in what was to become Montana Territory, with the first gold rush in 1862. In July of 1863, with the gold discoveries in Alder Gulch, McKay moved from Bannack to Virginia City. The following year, he moved on to Bivens Gulch where he purchased numerous mining claims with his Alder Gulch earnings. His Biven's Gulch claim employed up to 15 men at its height. He invested his mining fortune in farm lands in the Madison Valley, settling his family in Virginia City. The family did well in Virginia City. Alexander McKay participated as a life long Republican in local politics and economic development. In 1889 Mr. and Mrs. McKay moved to the Old Sarge Hall grist mill, near Sheridan, Montana. They remained at that site until their deaths.

In 1860 Alex McKay was married to Caroline Hanson in Kansas. Their first child, Flora, was born in 1861 near Denver, Colorado. In 1863, their second child Mary, was born in Virginia City. Flora and Mary attended Virginia City grade schools, then attended Iowa State College, where Flora received a degree of medicine and Mary a degree in music and art. Flora married Dr. C.A. McNulty in 1884. She later recieved a doctor of science degree from the Women's Medical College of Chicago, and a Master of Arts from Iowa College in 1893. Both Mary and Flora spent most of their lives in the Virginia City-Sheridan area and were very active in local social and religious organizations. Upon the death of their father, they helped Caroline McKay manage the family estate.

Alex McKay died in 1922. Caroline Hansen McKay died in 1917. Flora McKay McNulty and Mary McKay [Herhold, Bothwell] Swayze died within weeks of each other in 1945.