Interstate 17 is known as the Black Canyon Freeway from the northern end of the Phoenix Metropolitan Area to its first interchange with Interstate 10 northwest of Downtown Phoenix, which is known as The Stack. At the 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.
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.