In recent years, I have increasingly been asked by students why a mathematical field has developed in this particular way (usually presented in lectures) and not otherwise, what the main driving forces were, and how it will continue. In particular, alongside other factors such as applicability or connections to other fields, I was interested in the role that the major classical problems played in the development of a theory. The recent unusual solution to the 4-Color Problem provided me with a welcome opportunity to study the precise influence that this universally known problem primarily had on graph theory. Perhaps more than elsewhere, opinions diverge sharply on the 4-Color Problem. Some say that the mathematics that produced the 4-Color Problem is a marginal note, while the solution has had an enormous influence.