Katherine Duer Mackay
Katherine Alexander Duer Mackay (1878–1930) was an American suffragist, socialite, and writer from New York City. She founded the Equal Franchise Society (EFS) and became the first woman to serve on the Roslyn Union Free School District board. Her work helped show that wealthy women could play a major role in the suffrage movement.
Katherine was born in New York City in 1878. She came from a prominent family and married Clarence H. Mackay in 1898. The couple lived at Harbor Hill in Roslyn, New York, where Katherine became deeply involved in philanthropy and education. In 1899 she refurbished Roslyn’s public library, the William Cullen Bryant Library, improving its books and facilities and inviting the community to events.
From 1905 to 1910, Mackay served on the Roslyn School Board, the first woman on the board. She worked to end corporal punishment in the schools and believed that wealthy and poor should both participate in public education.
Her interest in suffrage grew after reading debates at the Colony Club. She supported maternalist ideas, arguing that giving mothers the vote would help protect their families and improve politics. In 1908 she founded and led the Equal Franchise Society, which aimed to win suffrage for women. She attracted wealthy supporters by hosting meetings at her home and recruiting members like Florence Harriman, Anne Harriman Vanderbilt, and Alva Belmont. The EFS organized lectures at the Garden Theater and helped fund the 1910 suffrage parade. Although she stepped back from the EFS presidency around 1911, she stayed involved as a member.
Her personal life was marked by public controversy. In 1913 she faced a lawsuit over alleged infidelity involving her husband and a physician, which helped lead to her divorce from Clarence in February 1914. She gave up her American citizenship and, in Paris, married Dr. Joseph A. Blake. The couple supported the war effort during World War I and returned to New York in 1919; they later divorced.
Even while abroad, Mackay continued to advocate for suffrage and supported the Woman Suffrage Party. She also wrote works, including a novel, The Stone of Destiny (1904), and a drama, Gabrielle, plus a piece published in The North American Review in 1903 titled A Dream from the Treasures Contained in the Letters of Abelard and Héloïse.
Katherine Mackay died in 1930 at about 51 or 52 years old. Her work helped change how society viewed suffragists and showed that influential women could lead social reform and inspire others to join the cause. She left a lasting legacy in Roslyn and in the broader fight for women’s rights. Her three children included Ellin Berlin.
This page was last edited on 3 February 2026, at 03:18 (CET).