George Dantzig, Ray Fulkerson, and Selmer Johnson solved a 49-city instance of the TSP in 1954 (they actually work with a 42-city instance by noting that the shortest route between Washington, D.C. and Boston passes through seven other cities in their list). Their work was a major breakthrough in the development of solution methods for the TSP, and their ideas continue to be used by today's researchers. A brief description of their fundamental work can be found in Dantzig, Fulkerson, and Johnson's Cutting-Plane Method. A higher resolution version of the tour image can be found in the Pictorial History of the TSP.