Captain Samuel H. Beckwith (December 18, 1837 – December 6, 1916) was a telegraph and cipher officer to Ulysses S. Grant. He was nicknamed "Grant's Shadow" by other staff officers. Beckwith was the first to transmit news of John Wilkes Booth's whereabouts after Lincoln's assassination, leading to his capture. Beckwith was also present as Grant's telegraph officer on Abraham Lincoln's visits.
In Washington, Lincoln used to daily visit the telegraph office, and cipher operator David Homer Bates was later to recall these visits, along with the testimony of Thomas T. Eckert, Charles A. Tinker, Albert B. Chandler, and Albert E. H. Johnson in Lincoln in the Telegraph Office (1907).