<Tr> <Th> NRHP Reference #</Th> <Td> 10001198 </Td> </Tr> <Tr> <Th> Added to NRHP </Th> <Td> February 17, 2011 </Td> </Tr> <P> The Arroyo Seco Parkway, formerly known as the Pasadena Freeway, is the first freeway in the Western United States . It connects Los Angeles with Pasadena alongside the Arroyo Seco seasonal river . It is notable not only for being the first, mostly opened in 1940, but for representing the transitional phase between early parkways and modern freeways . It conformed to modern standards when it was built, but is now regarded as a narrow, outdated roadway . A 1953 extension brought the south end to the Four Level Interchange in downtown Los Angeles and a connection with the rest of the freeway system . </P> <P> The road remains largely as it was on opening day, though the plants in its median have given way to a steel guard rail, and most recently to concrete barriers, and it now carries the designation State Route 110, not historic U.S. Route 66 . Between 1954 and 2010, it was officially designated the Pasadena Freeway . In 2010, as part of plans to revitalize its scenic value and improve safety, the California Department of Transportation (Caltrans) restored the original name to the roadway . All the bridges built during parkway construction remain, as do four older bridges that crossed the Arroyo Seco before the 1930s . The Arroyo Seco Parkway is designated a State Scenic Highway, National Civil Engineering Landmark, and National Scenic Byway . It was listed in the National Register of Historic Places in 2011 . </P>

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