MISSOURI ROUTE 66. The old road enters Ozark Mountain Country almost immediately while heading west through Missouri, and the modern day 66 traveler can't help noticing the differences in road grades with Interstate 44 when the two roads run side by side. It some parts, it's a real roller coaster ride up and down the hills of 66, while nearby I-44 drivers enjoy a relatively flat road, with only gradual upward inclines and descents. As the roads continue, both interstate and two lane traveler alike will notice and appreciate the impressive "rock cuts" through the mountains of Missouri.