Interstate 19


Interstate 19 is a short freeway in southern Arizona that connects Interstate 10 and Tucson with Nogales and Mexico. It is one of the shortest two-digit Interstate routes, with only Interstates 2 and 97 being shorter.

High Priority Corridor

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

Parallel/Historical U.S. Routes

Interstate 19 ultimately replaced the original routing of U.S. 89. Some old segments of U.S. 89 at Tucson and Nogales were incorporated into Business Loops for I-19.


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 most of 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 Arizona 86 / Ajo Way (Exit 99) and Interstate 10 (Exit 101) as part of the Interstate 10/19 Crossing interchange project. The 2004-installed signs use English units, while other replacements made since and further south retain the metric system. Vocal opposition from area business owners have countered efforts from the Arizona Department of Transportation to switch over to English units.2

A $54.3-million in construction upgraded the substandard trumpet interchange at Interstate 10. Commencing in June 2002, "The Crossing" rebuilt the former trumpet interchange 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 an overall Interstate 10 rehabilitation through the Tucson metropolitan area. A dedication ceremony held on August 7, 2004 marked the project completion.3

Highway Guides

Southern Terminus - Business Loop I-19 - Nogales, Arizona
Perspective from Interstate 19 south
The third to last mainline interchange of Interstate 19 is located at Mariposa with Arizona 189. All trucking interests to the country of Mexico must utilize this interchange to Arizona 189. Interstate 19 itself concludes in four kilometers, with the associated border crossing to Nogales, Sonora in six kilometers. Photo taken 05/25/03.
The second to last mainline interchange of Interstate 19 is Exit 1B with Western Avenue. The freeway continues for two short kilometers before merging with surface streets near downtown Nogales. Photo taken 05/25/03.
The last interchange of Interstate 19, Exit 1A with International Street departs the freeway in 500 meters. 1000 meters is all that remains of Interstate 19. Photo taken 05/25/03.
View of the last overhead signage of Interstate 19 Southbound. Nogales can be seen on the hill in the background, with Interstate 19 still orientated Southward at this point. Just ahead, the freeway curves to the left (east) towards the terminus in the below photo. Photo taken 05/25/03.
Descending toward downtown Nogales, Arizona. Traffic must reduce to 25 mph as Interstate 19 transitions into a surface street. The overhead in the above photograph indicated that a signal is ahead. This is not a traffic light however, just a yellow flasher advising motorists of pedestrian traffic. Photo taken 05/25/03.
The southbound conclusion of Interstate 19 occurs at this intersection. Note the lack of traffic lights or stop signs in place. The extreme southern segment of Interstate 19 ends in an east-west fashion. Ahead is the border crossing to Nogales, Sonora. The International border is easily discernible as the fence on the background hill. Also note the increased density of development on the Mexican side of the city. Photo taken 05/25/03.
Looking the other direction at the beginning of Interstate 19 northbound. There was no sign marking the beginning (nor was there an end sign either). In the far distance is the first exit signage on Interstate 19 Northbound for Western Avenue. Photo taken by Eric Harkness (07/01).
Entering Downtown Nogales at Business Loop I-19. This routing represents the original U.S. 89 through the city to Interstate 19 Exit 8. To the right is the International Border crossing. Mexico Federal Route 15 connects Nogales, Sonora with the provincial capital of Hermosillo. The Federal route continues southward all the way to Mexico City, some 1,350 miles to the southeast. Photo taken 05/25/03.
Northern Terminus - Interstate 10 - Tucson, Arizona
Perspective from Interstate 19 north
The last northbound Interstate 19 interchange is Exit 99 with Arizona 86/Ajo Way. Pictured on this sign bridge is the three kilometer guide sign for Exit 100, the northern terminus of the freeway at Interstate 10. Photo taken by Eric Harkness (04/02/05).
This photo shows the pre-construction scene on northbound Interstate 19 at Exit 99/Arizona 86 - Ajo Way. This east-west state highway travels westward to the Tohono O'Odham Nation and Arizona 85. 12 miles northwest of the terminus is the town from which Ajo Way gets its name. Interstate 19 has two remaining kilometers at this point. Photo taken by Eric Harkness (02/01).
Here are the replacement signs found along northbound Interstate 19 at Exit 99, Junction Arizona 86/Ajo Way. The Interstate 10 control city for all points east of Tucson is El Paso, Texas and not Las Cruces, New Mexico. Photo taken by Eric Harkness (04/02/05).
The left two lanes continue northwest onto westbound Interstate 10, while the right lane exits to Exit 101 (Junction Interstate 10 east to El Paso) and Exit 102, 22nd Street and 29th Street into downtown Tucson. This interchange was completely reconstructed during 2001-2005, and this photo shows the post-construction configuration of the interchange. Note the use of mileage rather than kilometers on these new advance signs. Photo taken by Eric Harkness (04/02/05).
Interstate 19 draws to a close at the upcoming gore point split for Exit 100A/B. As of May 2003, a detour for Interstate 10 westbound to Interstate 19 is posted. This is in association with the interchange reconstruction project. The detour takes motorists southward on Business Loop 19 at Exit 261 to Irvington Road (Exit 98). Photo taken by Eric Harkness (07/01).
Perspective from Interstate 10 east
The next two exits along eastbound Interstate 10 are 22nd Street/29th Street and Silverlake Road/Jct Interstate 19 south (one mile). Photo taken by Eric Harkness (04/02/05).
One mile west of Exit 260/Interstate 19 south before construction began. This stretch of Interstate 10 is heavily traveled with over 150,000 vehicles per day. Photo taken by Eric Harkness (07/01).
The left three lanes continue east on Interstate 10, while the right lane exits only onto southbound Interstate 19. Photo taken by Eric Harkness (04/02/05).
Interstate 19 departs toward Nogales here; eastbound Interstate 10 continues toward Benson. One mile east of Interstate 19 is the northern terminus of Business Loop I-19. This loop of Interstate 19 follows the original U.S. 89 alignment between Tucson southward to Green Valley at Exit 69 of I-19. Interstate 19 remains within the Tucson Metropolitan area for approximately 23 miles. Photo taken by Eric Harkness (04/02/05).
This eastbound Interstate 10 photograph shows some of the road construction in association with the Interstate 19 northern terminus redesign. All permanent guide signs have been removed due to the project as Interstate 10 squeezes through with only four lanes instead of the normal six. The construction sign indicates that Exit 260 departs in 0.25 miles. Photo taken 05/25/03.
A look at the future ramps to Interstate 19 south slightly further east than in the scene in the above photobox. Photo taken 05/25/03.
Access to Interstate 19 south from Interstate 10 eastbound was still in place at the time of this photograph. The westbound ramp to Interstate 19 however was closed at this time. Photo taken 05/25/03.
Perspective from Interstate 10 west
After the Business Loop I-19/6th Street exit, the next exit along westbound Interstate 10 is Exit 260, Junction Interstate 19 south to Nogales and Sonora, Mexico. Photo taken by Eric Harkness (04/02/05).
Westbound Interstate 10 reaches the transition ramp to Exit 260, Junction Interstate 19 south to Nogales. The left three lanes continue straight ahead. Photo taken by Eric Harkness (04/02/05).


  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.

Page Updated July 6, 2015.

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