This book gives an engaging overview of the advances in graph theory during the 20th century. The authors, all subject experts, considered hundreds of original papers, picking out key developments and some of the notable milestones in the subject. This carefully researched volume leads the reader from the struggles of the early pioneers, through the rapid expansion of the subject in the 1960s and 1970s, up to the present day, with graph theory now a part of mainstream mathematics. After an opening chapter giving an overview of graph theory and its legacy from the 18th and 19th centuries, the book is organized thematically into seven chapters, each covering the developments made in a specified area. Topics covered in these chapters include map colorings, planarity, Hamiltonian graphs, matchings, extremal graph theory, and complexity. Each chapter is supplemented with copious endnotes, providing additional comments, bibliographic details, and further context. Written as an accessible account of the history of the subject, this book is suitable not only for graph theorists, but also for anyone interested in learning about the history of this fascinating subject. Some basic knowledge of linear algebra and group theory would be helpful, but is certainly not essential.