Interstate 19

I-19 Arizona
North End
South End


Interstate 19 connects Nogales and Mexico with I-10 and Tuscon in southern Arizona. The freeway curves west around Crawford Hill from Grand Avenue (old U.S. 89) and the international border to bypass Downtown Nogales north to Arizona State Route 189. North from Rio Rico, I-19 parallels the Santa Cruz River to Tubac, Green Valley and the south suburbs of Tucson. The lone six lane section joins SR 86 with I-10 at South Tucson.

Costing $54.2 million, the Ajo Way Traffic Interchange project got underway in March 2016. Completed in Spring 2018, Phase I rebuilt the six-ramp parclo exchange with SR 86 and Ajo Way into a single point urban interchange (SPUI). Additional work added sound walls along I-19 from Ajo Way south to the Michigan Avenue pedestrian bridge. Started in July 2018, Phase II of the project expands southbound I-19 and constructs a braided ramp system between the Irvington Road off-ramp (Exit 98) and Ajo Way entrance ramp. Work on I-19 northbound adds an auxiliary lane from Irvington Road to SR 86 (Exit 99), sound walls, and a new pedestrian bridge at Michigan Avenue. Project II will take 18 months to complete and costs $29 million.4

High Priority Corridor

Interstate 19 from Nogales to Tucson is part of High Priority Corridor 26: CANAMEX Corridor.

Parallel U.S. Routes

Interstate 19 ultimately replaced the original route of U.S. 89. Some old segments of U.S. 89 at Tucson and Nogales were incorporated into Business Loops for I-19. The Tuscon business route was eventually decommissioned.


Interstate 19 opened initially from Rico Rico Drive (Exit 17) to Palo Parado Road (Exit 25) in 1966. The freeway was completed in 1979 when the section from Tubac (Exit 34) to Chavez Road (Exit 40) opened to traffic. See the I-19 Arizona guide for the rest of the time line.

One of the unique features of Interstate 19 is that the exit numbers and distance signs are based on the metric system, a first for the U.S. Interstate system. The use of metric units along I-19 was the result of a President Carter administration pilot project aimed to have the United States adopt the system. The metric units also served as a hospitality measure for Mexican tourists headed north to Tuscon and Phoenix.

Some of these metric signs were replaced between SR 86 / Ajo Way (Exit 99) and Interstate 10 (Exit 101) as part of the Interstate 10/19 Crossing interchange project. Signs installed during the project in 2004 used English units, while other replacements made since and further south retained the metric system. Vocal opposition from area business owners countered efforts from the Arizona Department of Transportation to switch all of I-19 over to English units.2

A $54.3-million in construction upgraded the substandard trumpet interchange joining I-19 with Interstate 10. Commencing in June 2002, “The Crossing” rebuilt the former exchange with new high-speed ramps and added connections to nearby 12th Avenue for I-10 and 29th Street / Silverlake Road for I-19. Work was completed as part the overall reconstruction of I-10 through the Tucson metropolitan area. A dedication ceremony on August 7, 2004 marked the project completion.3

Route Information

  • North End – Tucson, AZ

  • South End – Nogales, AZ

  • Branch Routes – 0

  • Mileage – 63.35

  • Cities – Nogales, Tucson

  • Junctions

Source: December 31, 2018 Interstate Route Log and Finders List

I-19 Annual Average Daily Traffic (AADT)

Southern Arizona – 1969

Initial portions of I-19 ran south from I-10 to Valencia Road (Exit 95) by 1965 and between Mariposa Avenue (Exit 4) and Palo Parado Road (Exit 25) by 1968.

The original trumpet interchange between Interstates 10 and 19 in Tuscon – 1972

U.S. 89, truncated south of Flagstaff as approved by AASHTO on June 15, 1992, was designated as Business Loop I-10 north of I-19 and as Business Loop I-19 south of I-10. The I-10 business loop was eventually decommissioned by the late 1990s.

Highway Guides

North End – Tucson, Arizona

Perspective from Interstate 19 north
Suburban frontage lines both sides of Interstate 19 from Irvington Road north to Ajo Way and Arizona 86. Button copy guide signs previously posted along this stretch were missing shields for both I-10 and AZ 86. Photo taken by Eric Harkness (04/02/05).
Interstate 19 north at the Ajo Way off-ramp (Exit 99), ahead of construction for The Crossing at I-10. Arizona 86 travels westward to the Tohono O’odham Nation to end at Arizona 85, 12 miles from the community of Ajo. Photo taken by Eric Harkness (02/01).
New signs were posted following the completion of The Crossing project along Interstate 19 north. The addition of Exit 102 provided access to Silverlake Road independent of the westbound mainline for I-10. Photo taken by Eric Harkness (04/02/05).
Two lanes default onto Interstate 19 west toward Phoenix as Exits 101 and 102 part ways from the right-hand lanes. I-10 angles southeast from South Tucson to Davis-Monthan A.F.B. while a frontage road north connects I-19 with 29th and 22nd Streets nearby. Photo taken by Eric Harkness (04/02/05).
Perspective from Interstate 10 east
An interchange sequence sign was the first indication for Interstate 19 south along I-10 east ahead of Exit 259. This stretch was reconstructed in 2008, with I-10 raised and expanded. Photo taken by Eric Harkness (04/02/05).
Button copy guide sign posted for Interstate 19 south, prior to The Crossing project rebuild. This stretch of Interstate 10 was heavily traveled with over 150,000 vehicles per day recorded at the time. Photo taken by Eric Harkness (07/01).
Interstate 10 continues east from Tucson to Las Cruces, New Mexico and El Paso, Texas while I-19 leads through the south suburbs and Green Valley. Photo taken by Eric Harkness (04/02/05).
Beyond Tucson, Interstate 10 travels to Benson in Arizona. Interstate 19 south remains within the Tucson Metropolitan area for approximately 23 miles. Photo taken by Eric Harkness (04/02/05).
Perspective from Interstate 10 west
Passing under 6th Street (former U.S. 89 and Business Loop I-19) south, one half mile ahead of Exit 20 for Interstate 19 south to Nogales and Sonora, Mexico. Photo taken by Eric Harkness (04/02/05).
A high flyover takes travelers south from I-10 west to Interstate 19 south at Exit 260. All guide signs here were replaced to use Clearview font after 2008. Photo taken by Eric Harkness (04/02/05).

South End – Nogales, Arizona

Perspective from Interstate 19 south
All trucking interests to the country of Mexico are directed to use Arizona 189 (Mariposa Road) south from Interstate 19 at Mariposa and Exit 4. The freeway continues south another 3.1 miles to west Street. Photo taken 05/25/03.
Western Avenue crosses paths with Interstate 19 at Exit 1B near Ephraim Canyon. The remaining 1.1 miles of I-19 curve east around Crawford Hill to Sonoita Avenue for Downtown Nogales. Photo taken 05/25/03.
Exit 1A departs in a third of a mile for International Street, which parallels the border west from Sonoita Avenue to a nearby neighborhood. Interstate 19 ends in 0.6 miles otherwise. Photo taken 05/25/03.
Cerro Pelon rises in the distance as Interstate 19 turns east to the Nogales street grid at West and Compound Streets. Photo taken 05/25/03.
Speed limits reduce to 25 miles per hour as the freeway transitions onto Compound Street through a commercial area west of Downtown Nogales. Photo taken 05/25/03.
Although unmarked here, Business Loop I-19 begins and follows Compound Street east and north to Sonoita Avenue north and Crawford Street east to Downtown Nogales. Photo taken 05/25/03.
Crawford Street takes Business Loop I-19 two blocks east from Sonoita Avenue to Arroyo Boulevard / Grand Boulevard (old U.S. 89). The International Border crossing is located just to the south. Mexico Federal Route 15 connects Nogales, Sonora with the provincial capital of Hermosillo. The highway continues southward all the way to Mexico City, some 1,350 miles to the southeast. Photo taken 05/25/03.
Perspective from Compound Street west
There are no signs marking the freeway beginning of Interstate 19 on Compound and West Streets. I-19 meets Western Avenue in 0.6 miles. Photo taken by Eric Harkness (07/01).


  1. “Some I-19 metric signs going,” Tucson Arizona Daily Star, January 19, 2004.
  2. “Arizona highway signs in metric units may change.” The Arizona Republic, October 5, 2014.
  3. Building the I-10/I-19 Traffic Interchange, Arizona Department of Transportation project web site.
  4. Southcentral Districts Projects – Interstate 19: Ajo Way Traffic Interchange. Arizona DOT project web site. Page originally accessed on April 21, 2017.

Page updated April 21, 2017.