Many years before automobiles and paved highways, Thomas Jefferson envisioned a grid system of roads across the United States. In 1925, a governmental board laid out interstate routes loosely based on the grid system. East-West routes were even numbered while North-South routes were given odd numbers.
A need for a route from Chicago to Los Angeles was apparent. The intended route was to head south from Chicago to Springfield, Illinois and then directly west to California. Cyrus Avery, an influential member of the committee, convinced the other committee members that a more southerly route through the flatlands of Oklahoma, Texas, New Mexico, Arizona and into California would be cheaper to build and also have the advantage of being an “all weather” road by avoiding the high Rocky Mountains which would have been crossed by the more northerly path. According to the grid pattern being followed, 62, 64 and 66 were available designations. Kansas used 62 for a secondary road so the board submitted its plan for Route 66. Approval came in 1926 and the rest is history.