As I-40 replaced US 66, the old highway's popularity greatly declined. Business along the route began declining as fewer and fewer people drove through the old towns. Slowly, many towns declined or were outright abandoned and became ghost towns, including tourist towns like Two Guns. Many residents of the declining US 66 towns described the loss of business being instantaneous, happening right after the bypasses opened. The Interstate bypasses also meant the end of US 66 as an active highway, in conjunction with California concurrently removing its section of US 66 from the state highway system between 1964 and 1974, which moved the western terminus of the entire highway to the Colorado River in Topock, Arizona. The same year, US 66 was also truncated in the east from Chicago to Joplin, Missouri.