Abstract
In the 1930s, Hassler Whitney observed that concepts such as independent sets, rank, and basis make sense not only in linear algebra, but also in graph theory. By isolating their key properties, he arrived at the notion of a matroid, and developed the basics of matroid theory, including duality.
We examine the contents of his landmark paper published in 1935, and briefly describe some subsequent papers by Takeo Nakasawa, Garrett Birkhoff, Saunders Mac Lane, and Richard Rado. Along the way, we point out the relations between matroids and lattices, configurations in projective geometry, and the greedy algorithm.