But in March, just about the time that the pair were going out on their 40th date in 40 days, Sandra got a letter from Rehnquist, telling her he wanted to see her to talk about “important things.” And in a March 29 letter, he popped the question. “To be specific, Sandy, will you marry me this summer?”

The future chief justice of the United States was proposing to the woman who years later would become the first woman to serve on the nation’s highest court.

The reveal comes in a new book entitled First by author Evan Thomas, set to be published in March 2019. Thomas, while doing his research, found the Rehnquist letters among O’Connor’s correspondence.