I want to know the answer to the following question:
What is unusual about I-19?
All the background I'm provided with is that "Interstate 10, which runs southeast to northwest through town, connects Tucson to Phoenix to the northwest on the way to its western terminus in Santa Monica, California, and to Las Cruces, New Mexico and El Paso, Texas toward its eastern terminus in Jacksonville, Florida. I-19 runs south from Tucson toward Nogales and the U.S.-Mexico border.". Is that enough to answer the question?
Answer: no