I am almost finished with a book about Humboldt (Invention of Nature by Andrea Wulf). It's been a fantastic read, and I was surprised/ashamed that I hadn't known anything about Humboldt until earlier this year.
Humboldt is strangely forgotten these days. He was an enormous figure in his time and soon after, in the 19th century. An ideal heir to the Age of Enlightenment. There's places named for him all over the world. But now his name mostly gets a confused shrug.