Mercedes Frances Deiz, née Lopez, was born in New York in 1917. Her mother was Czechoslovakian, and her father was Afro-Cuban. She graduated from high school at 16, and worked cleaning dressing rooms at a specialty store before finding a job as an usher and telephone operator at the Lafayette Theatre in Harlem. She continued to work at the theater after she began attending Hunter College in 1936, and it was during this time that she met Billy Owens through the theater. They married in 1937, and Deiz continued to attend Hunter College through 1939, but, because she was often supporting both herself and her husband, she left before finishing her degree. She found a job in office work for the Hotel and Club Employees Union, and in 1943, the couple had a son.

In 1948, Deiz traveled with her son to Portland, Oregon, where one of her brothers lived, in order to obtain a divorce, and decided not to return to New York. During her early life in Portland, she became active with the NAACP and the Urban League after being refused service at a drive-in restaurant. She found a temporary job at the Internal Revenue Service, where she met Carl Deiz, who also lived in Portland; they married in 1949 and later had two children.

Just after they married, Mercedes Deiz began a job in the law library at the Bonneville Power Administration, where she stayed until 1953, and then began work as a legal secretary for Graham Walker in 1954. Walker encouraged her to become a lawyer, and paid the tuition for her first semester at the Northwestern College of Law. She earned her law degree in 1959, and in 1960, she became the first Black woman admitted to the Oregon Bar. She practiced law in Portland until 1967, when she became a hearing officer for the Oregon Workman's Compensation Board, the first woman to hold that position. In 1969, Governor Tom McCall appointed Deiz to the U.S. District Court of Oregon, making her the first woman of color to be a judge in Oregon. In 1972, Deiz was elected to a new Multnomah County Circuit Court position that had jurisdiction over juvenile and family cases, defeating seven male opponents and becoming the first Black circuit court judge in the state. She served on the bench until 1992, the year she turned 75 and was required by law to retire.

Deiz was active in many civic and legal organizations during her career, including as a founding board member of Oregon Women Lawyers, and received myriad awards and honors for her work. She died in 2005.

Sources: "Mercedes Deiz," by Diane Ryerson, Oregon Encyclopedia, https://www.oregonencyclopedia.org/articles/deiz-mercedes; "A Life of Firsts," by Cliff Collins, Oregon State Bar Bulletin, December 2005, accessed June 14, 2024, https://www.osbar.org/publications/bulletin/05dec/heritage.html; information provided by Deiz in an oral history interview, SR 1256, Oregon Historical Society Research Library, https://digitalcollections.ohs.org/sr-1256-oral-history-interview-with-mercedes-deiz