Monterrey is the capital and largest city of the northeastern state of Nuevo León, Mexico, and the ninth largest city and second largest metro area in Mexico behind Greater Mexico City. Located at the foothills of the Sierra Madre Oriental, Monterrey is a major North American business and industrial hub, as well as the most populous city in Northern Mexico.

Saltillo is the capital and largest city of the northeastern Mexican state of Coahuila and is also the municipal seat of the municipality of the same name. Mexico City, Monterrey, and Saltillo are all connected by a major railroad and highway. As of a 2020 census, Saltillo had a population of 879,958 people, while the population of its metropolitan area was 1,031,779, making Saltillo the largest city in the state of Coahuila, and the 14th most populated metropolitan area in the country.