Sandra Day O’Connor—the first woman to serve on the Supreme Court—apparently turned down a marriage proposal from William Rehnquist, who would go on be chief justice, when they studied together in the 1950s. The revelation comes from author Evan Thomas, who found letters between the two during his research for a book. NPR reports Sandra Day entered Stanford Law School in 1949, aged 19, and began to date classmate Rehnquist, then 26, during their second year of studying together. Rehnquist graduated a semester early and left for a Supreme Court clerkship, but soon after sent a letter to Day telling her he wanted to see her to talk about “important things,” then wrote shortly afterward: “To be specific, Sandy, will you marry me this summer?” Their friends and colleagues were reportedly oblivious to the proposal until now. O’Connor and Rehnquist remained close friends until his death in 2005.