Interstates in Arizona
Arizona quickly adopted the then-new Interstate System in 1956 with open arms and quickly accepted the primary I-10 and I-40 routes. Unlike the US Highway System, federal aid was guaranteed for the Interstates: enough for every Interstate to be limited access. This posed some problems however in the 1970's when freeway revolts were common. That stopped freeway projects like the Papago Freeway in Phoenix from being completed, leaving I-10 on an older, more dangerous freeway. A lot of these issues were resolved in the 1980's and 1990's however, and the construction of the Papago continued.
With freeway revolts in the rearview mirror, Phoenix grew exponentially in size (partly due to the Interstate). This led to more freeways and Interstates being needed for fast and safe travel for the booming population. I-10 is still the backbone in the Valley of the Sun, as well as the Tucson area. I-19 is a very strange route itself, being completely signed in the metric system instead of the standard system.
- Interstate 10 - Signed in the 1950's and 1960's with major realignments well into the 1990's, I-10 is considered the backbone of the Phoenix Freeway System and Phoenix itself.