Final answer:
The influential German geographer and natural scientist of the early 19th Century was Alexander von Humboldt, whose work inspired many subsequent naturalists and intellectuals.
Step-by-step explanation:
The German geographer and natural scientist referred to in the question is Alexander von Humboldt. He was indeed one of the most influential figures of the early 19th Century. Humboldt's extensive travels and comprehensive writings had a significant impact on a wide array of naturalists and intellectuals such as Jefferson, Thoreau, Emerson, Darwin, and Goethe. His approach combined empirical observation with a philosophical view of nature, which was groundbreaking at the time. Humboldt's work predated Darwin's theory of evolution, but his understanding of the interconnectedness of nature laid a foundation for later scientific study in ecology and biogeography.