Barstow is a city located on Route 66 in California, with a population of around 23, 000. Amarillo is a city located on Route 66 in Texas, with a population of around 200, 000. AmarilloTexas is a combined metropolitan area of Amarillo and Texas, with a population of around 270, 000. TulsaOklahoma is a combined metropolitan area of Tulsa and Oklahoma, with a population of around 1 million. StLouisMissouri is a combined metropolitan area of St. Louis and Missouri, with a population of around 2.8 million.