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Interstate 17
Total length: 146 miles (235 km)
Southern terminus: Phoenix, AZ, at JCT I-10
Northern terminus: Flagstaff, AZ, at JCT I-40
States traversed & length in each:
- Arizona — 146 miles (235 km)
Major cities along route:
- Phoenix, AZ
- Flagstaff, AZ
Junctions with non-related Interstates:
Related loops and spurs:
Length I’ve traveled: Entire length
Time zones:
Mountain — Entire length
NOTE: Arizona does not observe Daylight Saving Time. All of Interstate 17 in Arizona is on Mountain Standard Time (UTC–7:00) year round.
Counties traversed:
Arizona — Maricopa, Yavapai, Coconino
A quick hypertext drive: Interstate 17 exists entirely in Arizona, serving to connect the cities of Phoenix and Flagstaff. I-17 actually begins at mile post 194 at its southern terminus; this results from an old signing practice in Arizona in which routes that began at another route (not the state line) were assigned mile posts that began at whatever mile they broke off the second highway. (Most of I-17’s current routing was once part of Arizona state route 69, which inherited a starting mile post of 201 from US 89. This former AZ 69/US 89 junction is just north of the current I-10/I-17 interchange northwest of downtown Phoenix. Later, I-17 was extended seven miles to the south and east through Phoenix, resulting in the 194 starting mile post.)
After splitting from Interstate 10 on the southeast side of downtown Phoenix, I-17 heads west and then curves north for another meeting with I-10. The stretch through the northern Phoenix suburbs and northern Maricopa County can frequently become congested; much growth has occurred here since I-17 was built, and the highway needs some widening here. Perhaps 50 miles north of Phoenix, I-17 begins to climb from the “Valley of the Sun” up to around 4,000 ft. (1,219 m) elevation, and stays in relatively mountainous terrain for about 35 miles up to the town of Camp Verde, descending a short but steep grade as it approaches that town. The highway then ascends back out of the Verde Valley and stays fairly flat for about another 20 miles or so, then climbs another long grade to reach an elevation of almost 7,000 ft. (2,133 m) about 30 miles south of Flagstaff. The last 30 miles are fairly flat at this high elevation, with more alpine vegetation (evergreen trees, etc.) taking over for the desert vegetation (scrub grasses, saguaros, etc.) found farther south.
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