Editing Interstate 17 (section)

==History==

The I-17 corridor roughly follows the first stagecoach route through the Black Canyon, established in 1878 between Cañon (now Black Canyon City) and Prescott. A later highway through White Spar from Wickenburg to Yarnell was improved in 1925 and incorporated into US&nbsp;89 in 1926.<ref name="ADOTBlog-History">{{cite news |last=Corbett |first=Peter |date=September 21, 2018 |title=How the I-17 Black Canyon Freeway evolved from stage route to modern highway |url=https://azdot.gov/adot-blog/how-i-17-black-canyon-freeway-evolved-stage-route-modern-highway |work=ADOT Blog |publisher=Arizona Department of Transportation |accessdate=November 6, 2022}}</ref>

In 1936, SR&nbsp;69 was established as a state route from Phoenix north to [[Prescott, Arizona|Prescott]].<ref name="1938 map">{{cite map|publisher=[[Rand McNally]]|title=Arizona and New Mexico Road Map|year=1938|url=http://www.arizonaroads.com/maps/index.html|access-date=November 27, 2011}}</ref><ref>{{cite web|url=http://www.azhighwaydata.com/resolutions/?syear=&submit1=Submit&eyear=&crc=3&rtnum=69&page=4|author=Arizona Department of Transportation|author-link=Arizona Department of Transportation|access-date=April 22, 2008|title=ADOT Right-of-Way Resolution 1936-P-624}}</ref> The road was completed by 1940 to Prescott. In 1954, a new route north to Flagstaff was established as SR&nbsp;79. In May 1956, the Black Canyon Highway from Phoenix to Flagstaff was completed,<ref name="ADOTBlog-History"/> but not to Interstate standards.<ref name="1961 map">{{cite map |publisher=[[Rand McNally]] |title=State Highway Department Road Map of Arizona |year=1961 |url=http://www.arizonaroads.com/maps/index.html |access-date=November 27, 2011}}</ref> It was incorporated into the new [[Interstate Highway System]], established by the federal government later that year, and designated as part of I-17.<ref name="ADOTBlog-History"/>

The first interchange on the Black Canyon Freeway was built in 1950 west of downtown Phoenix and was extended to Grand Avenue in 1957.<ref name="AZ-First">{{cite news |last=Nothaft |first=Mark |date=February 21, 2017 |title=Which freeway came first in the Valley? |url=https://www.azcentral.com/story/news/local/phoenix-contributor/2017/02/21/which-freeway-came-first-valley/97871258/ |work=[[The Arizona Republic]] |accessdate=November 6, 2022}}</ref><ref name="ADOTBlog-History"/> The freeway was extended to McDowell Road by 1971 and out of the Phoenix suburbs by 1974, at a cost of $33&nbsp;million.<ref name="AZ-First"/> By 1971, I-17 had been completed from Phoenix northward to Camp Verde where a short stretch had not been completed to standards. The stretch from [[Arizona State Route 279|SR&nbsp;279]] (now [[Arizona State Route 260|SR&nbsp;260]]) north to [[Arizona State Route 179|SR&nbsp;179]] was also complete. The largest section yet to be completed was from SR&nbsp;179 north to Flagstaff. This segment was still just a two-lane roadway, but it did have full traffic interchanges built at crossroads. The portion from I-40 south to the [[Flagstaff Municipal Airport]] had been completed by this time.<ref name="1971 map">{{cite map |publisher=Arizona State Highway Department |title=State Highway Department Road Map of Arizona |year=1971 |url=http://www.arizonaroads.com/maps/index.html |access-date=November 27, 2011}}</ref> The final section of I-17, near Camp Verde and Montezuma Castle, began construction in February 1977 and opened to traffic in August 1978.<ref name="ADOTBlog-History"/><ref>{{cite news |date=May 18, 1978 |title=Last Link of I-17 To Open in August |page=15 |work=[[The Arizona Republic]] |url=https://www.newspapers.com/clip/112675527/last-link-of-i-17-to-open-in-august/ |via=[[Newspapers.com]] |accessdate=November 6, 2022}}</ref>

In 1993, officials in Arizona proposed an extension of I-17 to connect with [[Interstate 15 in Utah|I-15]] in [[Utah]].<ref>{{cite news|url=https://www.deseret.com/1993/1/2/19024583/arizona-officials-seek-extension-of-i-17-into-utah|title=Arizona officials seek extension of I-17 into Utah|date=January 2, 1993|agency=[[Associated Press]]|publisher=[[Deseret News]]|access-date=January 27, 2021}}</ref>{{Clarify|date=February 2021}}

The existing interchange with Happy Valley Road in Phoenix was converted to a [[diverging diamond interchange]] (DDI). The project was finished in the fall of 2020.<ref>{{Cite web|url=https://www.azdot.gov/projects/central-district-projects/i-17-ti-reconstruction-happy-valley-rd-and-pinnacle-peak-rd/happy-valley-rd|title=Happy Valley Road|website=www.azdot.gov|access-date=2019-08-26}}</ref>

I-17 has the unusual distinction of starting at approximately milepost&nbsp;194 instead of at milepost&nbsp;0.<ref>{{cite map |author=Multimodal Planning Division |date=January 2014 |title=Phoenix Area Milepost System |url=https://apps.azdot.gov/files/CNS/F014701C/F014701C_Phoenix_Area_Milepost.pdf |publisher=Arizona Department of Transportation |accessdate=November 6, 2022}}</ref> 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.<ref>{{cite web |first = Caroline |last = Carpenter |title = Marking the Miles One Milepost at a Time |date = June 13, 2017 |url= https://azdot.gov/blog-article/marking-miles-one-milepost-time |work = ADOT Blog |publisher = Arizona Department of Transportation |access-date = January 30, 2025 }}</ref> I-17 inherited its milepost locations from [[Arizona State Route 69|SR&nbsp;69]], which the freeway replaced between Phoenix and Cordes Junction.<ref>{{cite news |last=LaBarbera |first=John |date=May 19, 2022 |title=Throwback Thursday: Future I-17 |url=https://azdot.gov/adot-blog/throwback-thursday-future-i-17 |work=ADOT Blog |publisher=Arizona Department of Transportation |accessdate=November 6, 2022}}</ref> SR&nbsp;69's mileposting was such that it coincided with [[U.S. Route 89 in Arizona|US&nbsp;89]]'s mileposting, which was 201.6 where the two routes intersected. When I-17 was constructed, the existing mileposting for SR&nbsp;69 was retained.<ref name="ADOT Highway Log"/>