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Colonel William Henry Greenwood was a distinguished American railroad engineer and Civil War mapmaker whose career spanned pioneering railway construction across the United States and Mexico. Born in Marlborough, New Hampshire, on March 27, 1832,  Greenwod graduated from Norwich University, the Military College of Vermont.

Greenwood’s railroad career began immediately after his graduation when he moved to Illinois to work with the American Central Railroad. By late 1852, he had relocated to Galva, Henry County, Illinois, where he was engaged in railway surveying and construction. 

With the outbreak of the American Civil War, Greenwood enlisted in the 51st Regiment Illinois Volunteers in 1862. He quickly rose to the rank of colonel, distinguishing himself not only as a line officer but also as a topographical engineer. His expertise in mapmaking and reconnaissance proved invaluable to the Union Army, leading to his appointment as an aide-de-camp to General David S. Stanley in the 1st Division of the IV Corps of the Army of the Cumberland. Greenwood participated in key battles, including Perryville, Stone River, Chickamauga, and Missionary Ridge, playing a crucial role in mapping terrain and coordinating troop movements. His skills in fortifications and rapid reconnaissance made him indispensable during the Atlanta Campaign, the Battle of Franklin, and the Battle of Nashville.

Following the war, Greenwood remained in military service, overseeing the reconstruction of the Gulf & San Antonio Railroad in Texas. 

After leaving military service, Greenwood became an influential figure in railroad expansion across the western United States. He became the general construction manager of the Denver and Rio Grande Railroad (D&RG), recruited by General William J. Palmer. As the general manager during the railroad’s push towards Cañon City, Colorado, he oversaw the construction of the first division, ensuring its success in expanding transportation networks through the rugged terrain of the Rocky Mountains. He later became the general superintendent of the railroad.

Greenwood’s expertise was also instrumental in the Kansas Pacific Railway’s surveying expedition of 1868. Alongside the Kansas Pacific’s chief engineer, he identified a strategic route through Pueblo, Colorado, the Royal Gorge, and the San Luis Valley, ultimately leading to Santa Fe, New Mexico. While the Kansas Pacific’s board ultimately chose a different route through Denver, Greenwood’s recommendations influenced future railway development in the region. 

In 1880, Greenwood accepted a high-profile assignment in Mexico, surveying a railway line between Mexico City and the Pacific Coast for the Palmer and Sullivan Company. This project was part of a larger effort to modernize Mexico’s transportation infrastructure and connect its interior with global trade routes. While conducting a survey near Rio Hondo, eighteen miles from Mexico City, Greenwood was ambushed and murdered on August 29, 1880.