Every year, usually in late winter, the New York novelist would write a letter to the great man. Whether hand-written or dictated and typed, the message was boldly signed, then sealed and addressed to the Czech Consulate at 1440 Broadway. From there it would be carried by special messenger to the Embassy in Washington, where it was pouched direct to Prague for the personal attention of the Founder-President himself. Upon opening the envelope, Thomas Garrigue Masaryk would find the familiar embossed initials on the letterhead —WSC. Willa Sibert Cather had written another letter.

Scholars have known for years that there was an extensive correspondence between Cather and Masaryk. She refers to it in a letter to a lifelong friend in 1945, suggesting that it was one of the most meaningful she had had with public figures. Until recently, no one had seen any part of the correspondence save for one letter of...