Famed American naturalist (1837–1921) best known for his writings on nature and travel. ALS, one page, 5.5 x 4.75, no date. Letter to Robert Underwood Johnson. In full: “When you send me proof of my May article, send duplicates—one to be retained by me. Let me have it as early as you can. How is Gilder?” Affixed to a same-size card. Intersecting folds slightly affecting the signature, a moderate overall shade of toning, and an ink notation to the bottom, otherwise fine condition. RR Auction COA.