 When war with Mexico seemed imminent , topographic engineers were sent to the border to assist with the army 's preparations . Raynolds served in Winfield Scott 's Mexican @-@ American War campaign which marched overland to Mexico City from the Gulf of Mexico seaport at Veracruz . After the war , the American army occupied Mexico City and the surrounding region . During the occupation , Raynolds and others set out to map and explore nearby mountains . Raynolds 's party is credited with being the first confirmed to climb to the summit of Pico de Orizaba ( 19 ° 01 ′ 48 ″ N 97 ° 16 ′ 12 ″ W ) which at 18 @,@ 620 feet ( 5 @,@ 680 m ) is the tallest mountain in Mexico and third tallest in North America . Over a period of several months , Raynolds and other officers from both the army and navy mapped the best approach route to Pico de Orizaba . To assist them in their climb , the party planned on taking <unk> attached to long ropes and primitive crampons in the form of shoes with projecting points to help ensure they could safely climb up cliffs and across glaciers . Told by local villagers that any attempt to reach the summit would be fruitless because no one had ever done it before , the Americans became even more determined to show the Mexicans it could be climbed . 
