The following article contains an answer for the question: What is the last name of the person who ascended the river in twenty one days as far as the first rapids in Pyramid Canyon? , can you please find it? 

Lorenzo Sitgreaves led the first Corps of Topographical Engineers mission across northern Arizona to the Colorado River (near modern Bullhead City, Arizona), and down its east bank to the river crossings of the Southern Immigrant Trail at Fort Yuma in 1851.The second Corps of Topographical Engineers expedition passed along and crossed the Colorado was the 1853-1854 Pacific Railroad Survey expedition along the 35th parallel north from Oklahoma to Los Angeles, led by Lt. Amiel Weeks Whipple.George A. Johnson was instrumental in getting the support for Congressional funding a military expedition up the river. With those funds Johnson expected to provide the transportation for the expedition but was angry and disappointed when the commander of the expedition Lt. Joseph Christmas Ives rejected his offer of one of his steamboats.  Before Ives could finish reassembling his steamer in the delta, George A. Johnson set off from Fort Yuma on December 31, 1857, conducting his own exploration of the river above the fort in his steamboat General Jesup.  He ascended the river in twenty one days as far as the first rapids in Pyramid Canyon, over 300 miles (480 km) above Fort Yuma and 8 miles (13 km) above the modern site of Davis Dam.  Running low on food he turned back.   As he returned he encountered Lieutenant Ives, Whipple's assistant, who was leading an expedition to explore the feasibility of using the Colorado River as a navigation route in the Southwest.  Ives and his men used a specially built steamboat, the shallow-draft U.S.S. Explorer, and traveled up the river as far as Black Canyon.  He then took a small boat up beyond the canyon to Fortification Rock and Las Vegas Wash.  After experiencing numerous groundings and accidents and having been inhibited by low water in the river, Ives declared: "Ours has been the first, and will doubtless be the last, party of whites to visit this profitless locality. It seems intended by nature that the Colorado River, along the greater portion of its lonely and majestic way,...

Johnson