I-19

About I-19

From Nogales, AZ (Mexico border) to Tucson, AZ (I-10)

Interstate 19 is a short north-south route in southern Arizona, running about 63 miles from Nogales on the Mexican border to Tucson, where it connects with Interstate 10. It is unusual in the Interstate system because its distance signs are posted in kilometers rather than miles, a legacy of a metric signing experiment. The route provides the main connection between Tucson and the border crossing at Nogales.

The highway runs through the valley of the Santa Cruz River, passing the communities of Rio Rico, Tubac, and Green Valley as it descends gradually from the border toward Tucson. It carries substantial cross-border trade and passenger traffic, including produce shipments entering through Nogales, and serves a corridor of historic and recreational sites in the Santa Cruz valley.

State-by-state mileage

State	Miles
Arizona	63.4
Total	63.4

History

Interstate 19 was designated in 1961 and built to link Tucson with the international border at Nogales. During construction the distances were signed in kilometers as part of a federal metric signage effort, and that practice has largely continued, making it the most prominent metric-signed route in the system.

The kilometer-based exit numbers and distance signs have been retained over the years, in part because of local familiarity and the cost of conversion.

Major cities and places

Notable features

• Santa Cruz River valley

Did you know

• Its distance signs are posted in kilometers rather than miles.
• It is one of the shortest one- and two-digit Interstates, at about 63 miles.
• It connects the border city of Nogales with Tucson and I-10.
• It carries heavy cross-border produce and trade traffic from Mexico.
• The route follows the valley of the Santa Cruz River.