Walter Lamb Nicholson (April 27, 1825 - April 13, 1895) was a topographer working with the United States Postal Service in the second half of the 19th century. Nicholson was born in Edinburgh, Scotland, where he trained as a civil engineer. He emigrated to the United States in 1856, registered for the draft in the American Civil War (1861 - 1865) in 1863, and naturalized as U.S. Citizen in 1873. By 1860 he was working in Washington D.C. as a lithographer with the U.S. Coast Survey, where he introduced photolithographic technology. On July 15, 1861, he transitioned to the Postal Department, where he succeeded Henry A. Burr (1809 - 1863) as official 'Topographer'. He issued numerous important postal route maps from about 1866 to his retirement in 1887. His postal maps continued to be used and updated by subsequent Postal Topographers until about 1900.