Interstate 19

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An intrastate route at just 63.35 miles in length, Interstate 19 begins in the city of Nogales, just north of the U.S./Mexico border. The freeway initially heads west before curving north along the Santa Cruz River all the way to Tucson. Along this historic river valley, the freeway passes Tumacacori National Monument, site of a historic Spanish mission. I-19 also travels through Green Valley, Sahuarita and the San Xavier Indian Reservation on this stretch.

Interstate 19 comtinues north to the south side of Tucson, where it converges with I-10 at The Crossing interchange adjacent to the city of South Tucson. I-10 links I-19 north with Downtown Tucson and east with Davis-Monthan Air Force Base. Interstate 19 directly replaced U.S. 89 and retained the milepost numbering of the U.S. highway.

Interstate 19 Arizona Guides

As part of the original design, the Arizona Department of Transportation (ADOT) received a waiver from Interstate Highway requirements to allow Interstate 19 to end in Nogales, rather than at the border. This was due to the topography of the Nogales area, and the disruption that the freeway would cause to the central business district, as discussed in a 1964 public meeting. The community wanted the freeway to end where Business Loop I-19 branches off (at Kilometer 8), or failing that, to be routed along the course of what became State Route 189 to the Border. The final decision resulted in I-19 taking the alignment it does today - the preferred alternative of the engineers.

Ironically in 2008, talks were held to discuss rerouting Interstate 19 away from the Central Business District of Nogales due to the traffic issues at the border.

Interstate 19 reflects design trends apparent during the construction period. The freeway was designed during the Lady Bird Johnson highway beautification era, and reflects it through the detailed landscaping and extra wide median.

Interstate 19 is also unique for being both the longest and only Interstate highway signed in Metric units. The signs were placed under a test program with the Federal Highway Administration (FHWA) with the completion of the freeway in May 1979.

ADOT announced in 2004 that the signs for I-19 were to be converted to English units, and replaced several assemblies around The Crossing interchange joining I-10/19. However in 2008, a new metric sign was placed outside Green Valley on southbound Interstate 19.

Subsequently in 2009, ADOT revealed that federal stimulus money would be used to re-sign the freeway, including renumbering all exits. Exit numbers however remain based upon kilometers, leaving I-19 and Delaware State Route 1 as the lone two routes nationally using the metric system for interchange numbering.

Construction Timeline:

  • Km 0 - 4 (Nogales - Mariposa Ave): 1971
  • Km 4 - 8 (Mariposa Ave - Business Loop I-19): 1968
  • Km 8 - 17 (Business Loop I-19 - Rio Rico Dr): 1968
  • Km 17 - 25 (Rio Rico Dr - Palo Parado Rd): 1966
  • Km 25 - 33 (Palo Parado Rd - Tubac): 1978
  • Km 33 - 40 (Tubac - Chavez Rd): 1979
  • Km 40 - 51 (Chavez Rd - Canoa Ranch): 1977
  • Km 51 - 69 (South of Canoa Ranch - Duval Mine Rd): 1976
  • Km 69 - 75 (Duval Mine Rd - Sahuarita Rd): 1972
  • Km 75 - 80 (Sahuarita Rd - Pima Mine Rd): 1971
  • Km 80 - 95 (Pima Mine Rd - Valencia Rd): 1969
  • Km 95 - 102 (Valencia Road - Interstate 10): 1965

Business Loop I-19

The one business loop for Interstate 19 joins the south end with Downtown Nogales along former U.S. 89. A second business route for I-19 followed old U.S. 89 south from I-10 in Tucson to Sahuarita. Established when U.S. 89 was truncated north to Flagstaff in 1992, Business Loop I-19 in Pima County was decommissioned in 2004.

    Connect with:
    Interstate 10
    State Route 86
    State Route 189
    State Route 289

    Page Updated 04-19-2022.

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