Back before the US 89A was built, there was State Route 79. State Route 79 was established in 1927, back then it was a graded dirt road. In 1940 the designation changed to US 89A to signify it as an alternate route to the US 89. State Route 79 ended up becoming the official designation for Pinal Pioneer Parkway road in 1991 which runs from Florence Junction to Oracle Junction.
While I'm unsure when the modern section of the 89A we know of today was constructed, there are still signs of the old alignment along this three mile drop into the canyon. If you are driving north and look up where this cache is, you can see old rock walls which I presume were part of the original road alignment.
This section of the old grade is 1/4 of a mile long. However, due to its age, plant growth, and erosion, walking along it is difficult. I was going to place this cache at the end near the rock fall area, but decicded against it as once you pass a certain point it becomes more of a bushwack than "road." There's a few old cans and bottles laying around here too.
FTF gets a unactivated travel bug. Have fun.