 During the research, he worked closely with Alexander von Humboldt, who had recently returned from his own South American trip, and could provide deep knowledge of the geography and science of the Americas and together they charted the route and first landing of Columbus in the Americas.Humboldt praised the biography after its release, which Walls, a biographer of Humboldt, partially attributes to Irving's willingness to pursue a wide-ranging scope of topics within the work, paralleling Humboldt's own effort, "Examen Critique".Historians have noted Irving's "active imagination" and called some aspects of his work "fanciful and sentimental".