Brief History of American Roads
Early roads in America were based on trade routes and exploration corridors. Local roads were and still are given names that often reflect the unique history and culture of the town. Increased population, vehicle speed, and roadway usage require levels of sophistication and so engineers and numerous construction workers are involved in the planning, grading, banking, paving, curving, and bridging of new roads.
A more complex system of state and federal highways brought about need for a system of rules for numbering interstates, byways, and highways. Interstate highways extending North-South have odd numbers with the number sequence increasing as you move in an easterly direction starting on the west coast.
For example, a road in California might be labeled Interstate 5, but by the time you reach the east coast of the U.S., you find Interstate 95. Interstates going East-West have even numbers with the highest number starting farthest North. Interstate 4, for example, runs across central Florida, west to east.