 As the expedition left to ascend the mountain , a long pack train of nearly fifty officers , soldiers and native guides departed from the town of Orizaba in early May 1848 . After several days of hiking through dense jungle , the expedition slowly gained altitude and established a base camp at 12 @,@ 000 ft ( 3 @,@ 700 m ) . Starting from base camp in the early morning of May 10 nearly two dozen climbers made the final push to the top of the mountain , but only Raynolds and a few others reached the summit . According to mountaineer and author Leigh N. Ortenburger , this feat may have inadvertently set the American mountaineering altitude record for the next 50 years . Raynolds estimated the summit of Pico de Orizaba to be 17 @,@ 907 ft ( 5 @,@ 458 m ) above sea level , which was slightly greater than previous estimates but below the modern known altitude . As no higher peaks were known in North America at that time , Raynolds believed Pico de Orizaba was the tallest mountain on the continent . The summit crater was covered in snow but estimated to be between 400 to 650 yards ( 370 to 590 m ) in diameter and 300 ft ( 91 m ) deep . The American achievement was disputed by the Mexicans until an 1851 French expedition discovered an American flag on the summit with the year 1848 carved in the flagpole . 
