Montague Lyon (1864-1942) was a prominent St. Louis lawyer. He graduated from Central High School in 1880 and from Washington University with a Bachelor of Philosophy in 1884. Upon graduation, he read law with the firm of Dyer, Lee & Ellis until he was admitted to practice as an attorney and counselor in December 1886. He later operated a private law practice, specializing in the legal affairs of street railroads and other corporations.

Montague was the son of German immigrants Henry David Lyon (1826-1888) and Caroline Marks Lyon (1826-1908), who arrived in the United States circa 1850 and were naturalized in 1857. Henry worked in St. Louis as a dry goods merchant and in the clothing industry. He also served as president of the United Hebrew Congregation of St. Louis in 1875.

Frances Robnett Smith Lyon (1872-1937) was born in Martinsburg, Missouri to Thomas Smith and Mary Frances Turk Smith. She graduated from Hardin College in Mexico, Missouri.

Montague and Frances were married in St. Louis on August 30, 1894. They had at least three children: Montague, Jr. (1896-1969); Randolph; and Mildred.