Martha Louise Black, née Munger, was born in Chicago, Illinois, to a prosperous family. She was educated at Saint Mary's College, a Catholic school in Indiana. In 1887, at about age 21, she married Will Purdy, with whom she had three sons. The couple made plans to join the Klondike Gold Rush northwestern Canada in 1899, but her husband backed out, taking a better offer of work in Hawaii. Martha, who was pregnant with her third child, chose to go to the Klondike with her brother instead and never saw Purdy again. She earned a living staking gold mining claims and running a sawmill. In 1904, after several years of courtship, she married her lawyer George Black, who later became Commissioner of the Yukon.
In 1921, Black was elected a Member of Parliament for the Yukon, a position he held until forced to resign due to ill health in 1935. Martha then ran for the seat in his place, and at age 69, became only the second woman ever to be elected to the Canadian Parliament. She published an autobiography, My Seventy Years, in 1938, later updated posthumously and republished in 1998 as Martha Black: Her Story from the Dawson Gold Fields to the Halls of Parliament.