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 million, the Ajo Way Traffic Interchange project got underway in March 2016. Completed in March 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.4 Started in July 2018, Phase II of the project expanded southbound I-19 and constructed a braided ramp system between the off-ramp at Exit 98 to Irvington Road and the entrance ramp from Ajo Way . Work on I-19 northbound added an auxiliary lane from Irvington Road to SR 86 / Exit 99, sound walls, and a new pedestrian bridge at Michigan Avenue by mid-January 2020. Costing $32 million, construction on Project II ran through Spring 2020.13,14
Interstate 19 from Nogales to Tucson is part of High Priority Corridor 26: CANAMEX Corridor.
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. A 6.8 mile long section between Chavez Siding Road and Canoa Ranch was finished in 1977.15 That left two segments to build and 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
Commencing in June 2002, a $54.3 million project replaced the substandard trumpet interchange joining I-19 with Interstate 10 in Tucson. Designed with longer ramps as well as improved geometry, the three level interchange at The Crossing was built slightly west of the original exchange.5 Work added ten bridges and eight ramps and reconstructed I-10 between 22nd Avenue and 10th Avenue and I-19 south to Ajo Way / SR 86. 12th Avenue was also rebuilt between 29th and 38th Streets and ramps from I-10 to 22nd Street were combined with new ones at 29th Street.6 Ramps were also added between I-19 and Silverlake Road.
Concrete columns supporting flyovers at the exchange, including the 60 foot high span from I-10 west to I-19 south, are decorated with maize and sunflowers. Painted tan, green and gold, the artwork represents the maize once grown by the Tohono O’odham tribe near the interchange location. The design was approved following a series of public meetings where different options were presented.7 The Crossings project was formally complete with a dedication ceremony held on August 7, 2004.8