American advocate for social and economic reform (1825–1909), and husband of Lucy Stone, with whom he helped found the American Woman Suffrage Association. ALS signed “H. B. Blackwell,” one page, lightly-lined, 5 x 5.25, March 6, 1883. Response to an invitation. In part: “It will give Mrs. Lucy Stone and Mr. H. B. Blackwell great pleasure to accept the kind invitation…to meet Mr. Whittier and a few of the early abolition friends on Thursday.” Affixed to a slightly larger sheet. In fine condition. RR Auction COA.