Foothill Boulevard is a major road in the city and county of Los Angeles, as well as an arterial road in the city and county of San Bernardino, stretching well over 60 miles (97 km) in length, with some notable breaks along the route. Like its name implies, Foothill Boulevard runs across the foothills of the San Gabriel and San Bernardino Mountains.

Los Angeles, often referred to by its initials L.A., is the most populous city in the U.S. state of California. With roughly 3.9 million residents within the city limits as of 2020, Los Angeles is the second-most populous city in the United States, behind only New York City; it is also the commercial, financial and cultural center of Southern California. Los Angeles has an ethnically and culturally diverse population, and is the principal city of a metropolitan area of 13.2 million people. Greater Los Angeles, which includes the Los Angeles and Riverside–San Bernardino metropolitan areas, is a sprawling metropolis of over 18 million residents.