William F . Raynolds William Franklin Raynolds ( March 17 , 1820 – October 18 , 1894 ) was a U . S . Army officer , explorer , engineer , Mexican War and Civil War veteran who is best known for leading the 1859 - 1860 Raynolds Expedition while serving as a member of the U . S . Army Corps of Topographical Engineers . Raynolds was also promoted to temporary Brevet Brigadier General in 1865 for meritorious services during the Civil War and retired from the Corps of Engineers a full Colonel on March 17 , 1884 , after a 40 - year military career . During the 1840s and 1850s , and again after his participation in the American Civil War , William Raynolds was the head engineer on a number of lighthouse construction projects as well as riverway improvements . In 1846 , while stationed in Veracruz , Mexico immediately after the Mexican - American War , Raynolds and several other U . S . Army personnel were the first to summit Pico de Orizaba , the tallest mountain in Mexico , and inadvertently set what may have been the American alpine altitude record for the subsequent 50 years . In 1859 , Raynolds was placed in charge of the first U . S . Government sponsored expedition to venture into what was to later become Yellowstone National Park . A heavy snowpack from the preceding winter forced the expedition further south than originally planned . Consequently , the expedition become the first federally organized party to cross what is known as Union Pass , enter Jackson Hole and see the Teton Range , now within Grand Teton National Park . Early life . Born in Canton , Ohio , William Raynolds was appointed from his native state and entered the United States Military Academy at West Point , New York on July 1 , 1839 . Raynolds graduated fifth out of 39 classmates in his class of 1843 , which included William B . Franklin , friend Joseph J . Reynolds and future United States President Ulysses S . Grant . Military career . Initially appointed a Brevet Second Lieutenant in the 5th U . S . Infantry , Raynolds was transferred to a new branch of the Corps of Engineers , the Topographical Engineers , an officer - only unit which made surveys and maps for army use . Raynolds would serve in this branch for his entire career . Raynolds ' s first assignments involved improving navigation on the Ohio River and surveying the northeastern boundary of the United States . When war with Mexico seemed likely , topographic engineers were sent to the border to assist the army ' s preparations . Raynolds accompanied Winfield Scott and his staff to rendezvous off the port of Veracruz . Mexico War . Raynolds served in Scott ' s Mexican - American War campaign from Veracruz to the Mexican capital district but received no brevet promotions , unlike his West Point classmates Franklin and Grant . After the completion of the war , the American army occupied Mexico City for some months . Looking for adventure , Raynolds and a few of his fellow soldiers obtained permission to explore and map nearby mountains . Raynolds ' s party was credited for being the first to climb to the summit of Pico de Orizaba which at , is the tallest mountain in Mexico . This feat may have been the American mountaineering altitude record for the following 50 years . Lighthouse engineer . After returning from Mexico , Raynolds resumed the uncompleted task of mapping the Canadian border he ' d been surveying before the war , then embarked on a project to develop water resources for the nation ' s growing capitol at Washington , D . C . Next Raynolds traveled the Great Lakes for several years surveying and mapping shorelines while identifying potential lighthouse locations . After promotions to First Lieutenant and Captain , in 1857 Raynolds undertook the construction of a number of lighthouses along the Jersey Shore and Delmarva Peninsula . In less than two years Captain Raynolds supervised construction of the Fenwick Island Light , the Finns Point Front Range Light , the Cape May Light and the Absecon Light . Raynolds Expedition . In early 1859 Raynolds was charged with leading an expedition into the Yellowstone region of Montana and Wyoming to determine , " " as far as practicable , everything relating to . . . the Indians of the country , its agricultural and mineralogical resources . . . , the navigability of its streams , its topographical features , and the facilities or obstacles which the latter present to the construction of rail or common roads . . . " " . The expedition was carried out by a handful of technicians , including geologist / naturalist F . V . Hayden , who led several later expeditions to the Yellowstone region , and topographer James D . Hutton . The expedition was supported by a small infantry detachment and was funded with $ 60 , 000 by the U . S . Government . Experienced mountain man Jim Bridger was hired to guide the expedition . Though the Raynolds Expedition was unsuccessful in exploring the region that later became Yellowstone National Park , they were the first U . S . Government sponsored party to cross the mountain pass in the Wind River Range that Raynolds named Union Pass and enter Jackson Hole in 1860 . In 1859 , Raynolds reported that the once abundant Bison were being killed for their hides at such an alarming rate , that they might soon become extinct . The outbreak of the American Civil War and a severe illness afterwards delayed Raynolds from presenting his report on his 1859 - 1860 expedition until 1867 . American Civil War . Raynolds returned to Washington at the outbreak of the war , and was made chief topographic engineer of the Department of Virginia in July , 1861 . The army lacked adequate maps for military use , so Raynolds and his team of engineers began to survey and draw useful maps of Virginia and the newly created loyal state of West Virginia . In 1862 , Raynolds was engaged as part of John C . Frémont ' s Mountain Department in chasing Stonewall Jackson up the Shenandoah Valley , being surprised by and losing to Jackson ' s forces at Battle of Cross Keys . Raynolds spent two months recovering from illness after the Valley Campaign , then was assigned as chief engineer of Middle Department and VIII Corps in January 1863 . Promoted Major in the Corps of Engineers from March 1863 , Raynolds found himself in charge of the defenses of vital Harpers Ferry , West Virginia during Robert E . Lee ' s second Confederate invasion of the north before the Gettysburg Campaign . As the end of war approached and hostilities with Sioux Indians loomed , Raynolds ' s knowledge and experiences of the Great Lakes area became more important to the army than his abilities commanding an ordnance depot . From April 1864 , while his classmate U . S . Grant was planning his Overland Campaign , Raynolds returned to the Great Lakes as superintending engineer of surveys and lighthouses . Raynolds supervised the siting of lighthouses like the Alpena Breakwater Light in Alpena , Michigan and dozens of others . Post war career . Raynolds was brevetted Brigadier General for his Civil War service and promoted to Lieutenant Colonel in the Corps of Engineers . He continued serving with the Corps of Engineers in a variety of harbor and river navigational improvements until his retirement in 1884 . Raynolds sited and oversaw the installation of dozens of lighthouses in the Great Lakes area . He erected more lighthouses along the Gulf Coast and again in New Jersey , such as the Hereford Inlet Lighthouse built in 1874 and the original New Castle Range Front and New Castle Range Rear Light houses in 1876 . After the Civil War , the Corps of Engineers undertook a massive program of river and harbor improvements . Raynolds supervised the dredging and improvement of navigation on western waterways of commerce like the Arkansas , Mississippi and Missouri Rivers . He was involved in harbor dredging and construction in Buffalo , New York , Harbor of Refuge in New Buffalo , Michigan , Erie Harbor in Erie , Pennsylvania , and the river harbors of St . Louis , Missouri and Alton , Illinois . As he approached retirement , Raynolds was elected trustee of the Presbyterian Church . Legacy . According to USMA classmate Joseph Reynolds , who saw William Raynolds at the USMA Association of Graduates reunion in 1893 , Raynolds had maintained a vigorous and healthy appearance even in extreme age , his brown hair " then but slightly sprinkled with gray . . . " Raynolds left his widow a substantial estate , estimated at his death in 1894 between $ 50 , 000 and $ 100 , 000 . After providing for his widow , his will directed that after her death , the entire estate would create a trust fund to assist Presbyterian churches in need . For a lifelong soldier who was engaged in few actual battles , Raynolds spent much of the first part of his career exploring the American western frontier , negotiating successfully with local Indian tribes , and drawing the first maps of areas now called the Dakotas , Wyoming and Montana . His improvements to harbors and navigation were undertaken to and undoubtedly did save lives . Hundreds of lighthouses sites selected by Raynolds are still in use ; dozens of lighthouses built by Raynolds still stand , and many still operate . The mountain gap where Raynolds ' s party crossed Continental Divide between Southwest Montana and Northeast Idaho is named Raynolds Pass in his honor , as is Raynolds Peak in the Teton Range .