Interstate 17  Interstate 17 (I-17) is a north–south Interstate Highway located entirely within the U.S. state of Arizona. I-17's southern terminus lies within Phoenix, at Interstate 10, and its northern terminus is in Flagstaff, at Interstate 40. The majority of I-17 is known as the Arizona Veterans Highway. In the Phoenix metropolitan area, it is mostly known as the Black Canyon Freeway, however the southern is part of the Maricopa Freeway. The portion of the highway south of Cordes Lakes was built along the alignment of SR 69, while the northern part was built along old SR 79's alignment. I-17 is one of the most scenic Interstate Highways as it gains more than a mile in altitude between Phoenix at and Flagstaff at . The highway features several scenic view exits along its route that overlook the many mountains and valleys found in northern Arizona. Interstate 17 is known as the Black Canyon Freeway from the northern end of the Phoenix Metropolitan Area to a point south of The Stack interchange with Interstate 10 northwest of Downtown Phoenix. (It is accompanied by frontage roads for most of this portion, and they carry the Black Canyon "Highway" name to distinguish from the "freeway" status.) At the Durango Curve southwest of downtown, between the 19th Avenue and Buckeye Road interchanges, it picks up the designation Maricopa Freeway all the way to the southern terminus at the second Interstate 10 junction. It is one of the metropolitan area's primary freeways. It has two interchanges with Interstate 10 in Phoenix. I-17 has the unusual distinction of starting at approximately milepost 194 instead of at milepost zero. This is a holdover from Arizona's old system of marking mileposts, where a branching route would continue the milepost numbering of its original host, instead of starting over at zero. Interstate 17 inherited its milepost locations from SR 69, which the freeway replaced between Phoenix and Cordes Junction. SR 69's mileposting was such that it coincided with US 89's mileposting, which was 201.6 where the two routes intersected. When I-17 was constructed, the existing mileposting for SR 69 was retained. I-17 is closed to bicycles and pedestrians south of Anthem Way (exit 229) in the Anthem area, but is open to them north of this point. In 1936, SR 69 was established as a state route from Phoenix north to Prescott. The road was completed by 1940 to Prescott.